I'll bet your '68 still had the 10.1:1 compression ratio, too, like my 1970 Electra did. After 1970 the compression ratio got whittled down to 8.5:1 a whole 15% less power per cylinder travel stroke in spite of the 455 cu in. (or in Cadillacs the 472 or 500 cu. in.)
My company cars are all 1970 Cadillacs of one sort or another now. They are all 10.1's
I was glad to see your picture of the ‘70 Electra. It is the missing link between my ‘68 and my fathers ‘73. The look of the ‘68 was smooth and elegant especially with the single body line that ran the length of it. My fathers ‘73 looked much more like the Cadillacs in your picture. Large and rectangular. The picture of the ‘70 Electra shows me how that body evolved from ‘68 to ‘73. Mine may have started out with 10.1:1. But after a late night highway trip with half the town in it I warped a head. I pulled the left bank cyl head in my driveway outside in January. Took it in to the parts store where I worked as the delivery driver. We took it to the machine and replaned it. I didn’t know any better and I reinstalled the head even though I knew there was damage to the top of piston #6. From then on I thought of it as a 7cylinder. Sometime after that I went to adjust the ignition timing and sheared the distributor off flush with block. But that is another story.