& for an example;
Post coupe & HT, is price point they get way more for a hard top
even back when cars were (68/69 RR) mid year $3,500 for a HT
& decent optioned $3,200 for a post coupe/pop out rear windows 'no window mechanisms'
(or some would call a sedan, if not a muscle car)
same body different glass, made by the thousands, roof skins same,
doesn't cost much more
but get 10%+ maybe %15 more actual profit in sales, by bean counting
for the MSRP
GM, at least Chevrolet, used the same bell housing across the six, small block and big block engine lines. I thought the distributors for small blocks also fit big blocks? I may be wrong there.
I'm still boggled by the post and hardtop models built concurrently. What is the reasoning there?
Yeah

I wish the BBM & SBM would have had same bellhousing/clutches & flywheels
many have or had the same starters
It would have made a lot of stuff simpler,
they probably saved $2+ in aluminum ea.
doing the smaller bolt patterns, after millions of them made,
that is a couple million $$s more profits,
for the penny pinchers
bean counters/accounting spread sheets,
it's that is what truly runs corporations
I did build a crapload of GM stuff, it was easier, in some ways
GM it's got some weird crap too,
like Olds vs Buick vs Pontiac
(all the 1st 3 had weird minor changes too, trans's & bolt or even wheels patterns etc.)
vs Opel (made for Buick) vs Chevy vs Caddy

until they went corporate & everything had a Chevy in it,
like starting in like 1993-94 (IIRC)
I'm pretty damn sure 'some bean counter' had something to do with that too
hell Canadian cars once were strange to us here,
Chevy's body platforms were Pontiac branded/Chevy bodys,
rebaged & regrilled, different trim etc. (not all but many)
but still what was our Chevy body styles in the lower 48
depends on what country they went too
some real kinky crap was going on back then
I'm sure 'some bean counter' helped make that decision too