Back in the day it was awsome to see actual production engines match up on the track...hemi's vs 429 boss vs 427.
Today all we get is identical aftermarked small blocks in slightly different fiberglass bodies...and don't forget Nascar has gone down soo far as to allow front wheel drive cars (Tempo) to compete.

Chevy was tooling up there own version too when Nascar changed it's engine rule.
If they wouldn't have, they'd be racing 600 cubic inch motors with 4 cams or something by now.
I guess you could say the Hemi was too good and ruined the party for everyone.

As far as fwd bodystyles, there weren't any rear wheel drive cars being made anymore so what was Nascar supposed to do?

Only the nose is fiberglass. The body's are steel.

The Ford SOHC was an Overhead Cam Engine, the four cams were driven by a HUGE chain. There were a couple engine failures because of this chain that caused considerable damage to the cars.
It was feared what could happen if a chain failed during a race and sent debris into a crowd or another car.
Since then the rule has been, that all engines in NASCAR must be or an Overhead valve, pushrod design.
It stacked up well against the Hemi in horsepower, but lacked durability.
The Boss 429 design saw lots of glory in the 60s and early 70s with the Wood Brothers and David Pearson.

It would have been an Awesome Match up had it been allowed to Happen!!!!!!!