Front seat re-mounting position

[Steve W]

So I was out for a little cruise the other day, pulled into get some gas, and as I was filling up, a rather tall-ish man (maybe 6'2"?) asked me how tall I was. I replied "about 6'5", and he said "well, I'm not that tall, but I have a '66 Cadillac I'm fixing up, and I'm surprized at the lack of legroom that car has, and I wondered how YOU fit".
 
I told him I felt the same way when I first got my car, but through my decades of owning classic cars, I always took my cars to a shop and had bars bolted, or welded, in that would allow me to relocate my seat farther back. (my 68 Camaro, my 66 GTO, my 65 T-Bird).

BUT, in the case of my Cadillac, I read in the service manual that Cadillac has two sets of mounting holes so that the dealer can adjust the seat to fit just about anyone, and that I had re-mounted my seat to the holes furthest back, and that, along with the 6 way power seat adjusted, was just about perfect! He said he never knew that, and did I think his '66 had that feature? I told him I honestly didn't know. But it made me curious.

When did Cadillac start this feature, and when did it end?

[Clewisiii]

For 1961 the body has one set of holes. But the seat riser foot has two.  Interesting that only one set id oversized.