Here's a picture of the '63 Tempest similar to the one I was looking at:
Compare it to the '63 GTO:
It ain't so 'little'. I have a friend with a restored Tempest of that vintage. It turns out it's quite a rarity. The reason is that a Tempest can be turned into a GTO by buying readily available knock-off parts that fit right on the Tempest. It then becomes a GTO - sort of. My friend says that a large number of restored 'GTOs' in auto shows are actually Tempests, based on the VINs, and restored Tempests don't ever show up.
The Tempest was introduced as an entry-level compact in September 1960 for the 1961 model year.
Sharing the new monocoque (unibody) Y platform with the Buick Special and Skylark, as well as the Oldsmobile F-85 and Cutlass, the Tempest also appeared under the LeMans nameplate (largely beginning with the 1962 model year, although Pontiac also manufactured a few 1961 LeMans coupes).
For 1964, the Tempest line was redesigned as one of the new General Motors mid-size automobiles that were built on the new GM A-body platform.
The Tempest name was discontinued after the 1970 model year in favor of LeMans, the nameplate that had previously designated the upmarket versions of the Tempest series.
In Canada, Pontiac also marketed a rebadged version of the compact L-body Chevrolet Corsica under the name Tempest from 1987 to 1991.
-snip-
In 1964, the Tempest was redesigned as a more-conventional vehicle and enlarged from a compact to an intermediate-sized car with a 115 in (2,900 mm) wheelbase and an overall length of 203 in (5,200 mm). The unibody, curved driveshaft and transaxle were gone; they were replaced by a traditional front engine, front transmission, frame and solid rear axle design used by all of GM’s other cars, with the exception of the Corvette and Corvair.
Together with its sister cars (the Oldsmobile F-85/Cutlass and Buick Special/Skylark), the Tempest/Le Mans moved to the new A body platform shared with the new Chevrolet Chevelle, and all three cars received updates and modifications standardizing them throughout—including the wheels—by GM edict. The Le Mans name was discontinued as a separate series, so now the cars were, in ascending order, base Tempest, Tempest Custom, and Tempest Le Mans.
Replacing the previous “Trophy 4” inline four-cylinder engine as standard equipment was a new 215 in³ Pontiac straight six with one-barrel carburetor and 140 hp (104 kW; 142 PS). This six was basically a smaller bore (3.75”) version of the 230 cu in (3.8 L) Chevrolet straight-6 offered as Pontiac exclusive.
Optional engines included two versions of the 326 in³ Pontiac V8 introduced the previous year, a two-barrel 250 hp (186 kW; 253 PS) regular fuel option; or the 280 hp (209 kW; 284 PS) 326 HO engine with four-barrel carburetor and 10.5:1 compression ratio which required premium fuel. Transmissions included a standard three-speed manual with column shift, four-speed manual with floor-mounted Hurst shifter or a two-speed automatic; the latter was a version of Buick’s Super Turbine 300.
The popularity of the high-performance 326/336 V8 package the year before prompted Pontiac to make it available again on the Tempest Le Mans and give it a name: GTO, after the Italian abbreviation “Gran Turismo Omologato” used to designate specially equipped cars homologated for racing.
Available with Pontiac’s largest V8, the 389 cu. in. (6.4L), and equipped with a four-barrel carburetor (producing 325 hp) or the soon to become iconic 345 hp 3 x 2 barrel set-up, the GTO proved to be the defining muscle car of the 1960s.
Unsurprisingly, the success of the GTO prompted Oldsmobile to rush out its own high-performance option package for the F-85/Cutlass called the 442, and the next year for Buick to release a high-performance version of the Skylark called the Skylark Gran Sport, or GS. Both cars would enjoy success and join Chevrolet’s Chevelle SS in GM’s effort to capitalize on the exploding muscle car era.
Engine offerings for the 1965 Tempest were the same as 1964, except the 326 HO was uprated to 285 hp (213 kW; 289 PS) and the GTO 389’s uprated to 335HP and 360HP via higher rise intake manifolds. Styling changes included a new split grille with vertical headlights similar to the larger Pontiacs, revised taillights and a more slanted rear deck. A two-door hardtop coupe was added to the Tempest Custom line, while the Le Mans got a four-door sedan with a plush interior done in Preston Cloth trim similar to the full-sized Bonneville Brougham.
A major facelift was made on the 1966 Tempest that included more rounded bodylines with a Coke-bottle effect similar to the full-sized Pontiacs. New four-door pillarless hardtop sedans were added to the Tempest Custom line. Under the hood, the Chevy-derived 215 six was replaced by a new 230 in^3 Pontiac overhead cam six, the only such engine found in an American production car at that time. This was also the first American-built engine to use a belt to time the camshaft to the crankshaft rather than a chain. The base OHC had a one-barrel carburetor and was rated at 165 hp (123 kW; 167 PS), designed for economy buyers.
Optionally available as part of the Sprint option package on two-doors was a four-barrel, high-compression 207 hp (154 kW; 210 PS) version of the OHC six, marketed as an alternative to higher-priced European sport sedans, which had similar OHC engines. For those wanting V8 power, the 326 and 326 HO options continued with horsepower ratings of 250 and 285 hp (213 kW; 289 PS), respectively, and GTO engines stayed the same.
Only minor changes were made to the 1967 Tempest, Custom and Le Mans models. The GTO 389 cu. in. V-8 was replaced by a new 400 cu. in. V-8. The Rochester 4bbl. carburetor replaced both the standard GTO Carter AFB 4bbl and the 3 × 2bbl. carburetor option. The Turbo Hydromatic TH-400 replaced the previous Buick Super Turbine two speed automatic. The 326 cu. in. V-8’s remained unchanged. The 4bbl. OHC six was uprated to 215 hp (160 kW; 218 PS).
Front disc brakes were a new option along with a stereo 8-track tape player and hood-mounted tachometer. All 1967 Pontiacs got GM’s safety package, mandated by Federal law, which included a dual-circuit braking system, energy absorbing steering column, wheel, and interior, shoulder belt anchors, four-way hazard flashers, and a new directional signal control that could be “flicked” for lane changes.
Here's a picture of the '63 Tempest similar to the one I was looking at:
Compare it to the '63 GTO: