Well, the hemi dominated the 64 season....with petty winning the championship easily...but he wouldn't even come back to defend his championship...
Basically it went like this:
It used to be that one needed to build x amount of cars in a certain configuration to homologate the car for a given season. And while Ford AND chrsyler were preparing to do so, Bill France came in and basically changed the rule at the last second...instead of x, one need double, so 2x cars built to meet the homologation standards to allow the cars to race. France knew by doing this, he was eliminating both the SOHC and Hemi's and said as much.
Most of the big name mopar drivers withdrew for the 65 season...some for the whole season, while others cherry-picked races they knew they could compete; mopar simply wouldn't support a race team that year in protest. Some raced, none with hemi's. Petty was one who would come in here and there to compete and win money, but w/ little support.
Ford was okay w/ that...and continued to support racing. And unquestionably, 65 was their most dominate season.
But it led to one of the neater instances...not terribly successful, but neat never-the-less: Petty became a full-time driver for his own drag team.
http://www.nascar.com/news/101130/re...965/index.html
The first car Petty drove was named "Outlawed" in response to France's edict. He also had a bumper sticker: "
NASCAR: If you can't outrun 'em, outlaw 'em."
Petty would lose the name though when his first barracuda was involved in a racing accident, and ended up killing an 8 y/o kid in the stands...
When mopar WAS allowed back with the Hemi (thanks in part due to negotiating and ensuring the hemi was available across the board---and thus no longer "just a racing engine"), it was with an exception...while most were transitioning to smaller mid-sized cars, Dodge/Plymouth would have to run full-sized Polara's and Fury's on the superspeedways...and running smaller charger, coronets, and belvedere's on the smaller tracks.
Since Ford wasn't allowed to come with it's SOHC, they then withdrew factory support for that 66 season...but would come back with the more aerodynamic cars to offset the hemi's advantage...which would then set off the aero wars.
As far as restrictor plates, it was the speeds of the cars...the winged mopars were regularly topping speeds of over 200 on the superspeedways, with some speeds for these guys hitting 220+. So in 71, a max displacement rule of 358ci was passed, and larger engines (which was pretty much all of them) had to run restrictor plates...up until 74, when big blocks were effectively banned from nascar.
Those were the days of Nascar racing imo...both 65 and 66 seasons suffered because while the fans loved the drivers, they also loved and cared about the cars that were racing. They loved the battle of Ford vs Mopar vs Chevy, olds pontiac, etc...
And it was because of this kind of racing that we have hemi's, rat engines (derived from the mystery motor), and sohc engines...their inclusion into drag racing was simply incidental to what was happening at nascar. (Interestingly, older engines such as the 406/427 side-oilers, 413/426 max wedges, 409's were necessitated by the need to compete in drag racing...but soon nascar took over). But, that need to homologate the cars is why Hemi's were available on most every dodge/plymouth made...and available to anyone who ponied up for the typically 850 dollar option.