Depends on the engine. In the '80s, it was Ford with the best V-8s and inline 6's (not sure if Chevy had that or not). The only real thing Chevy had was a good 350, and halfway decent 400s and 454s, but I don't know what vehicles those went in (if they went into anything). The 305 was horrific, as was anything smaller.
The Ford had a good inline 6, a great 302, a great 351, and a good 460 -- if you wanted something that measured in gallons per mile! Ford had better fuel injection back then as well.
Chevy had a really powerful, reliable 292 V6.
Ford still has better fuel injection.
One of the reasons Ford can use Toyota-patented technology on their hybrids is that Toyota is in turn allowed to use Ford-patented direct injection spark ignition technology on gas engines. That tech is one of the big reasons that the new Mazda CX7 and Mazdaspeed 6 are able to get 274 hp and 280 lb-ft out of a 2.3L I4 - and its torque curve is nice and flat - up to 95% of peak torque at redline.