'73 was a very eventful year for Pontiac. Some good & some bad. To me, the bad was the complete body style change for the A-body. That's all I'll say about that, because some here love the '73 A-body.
The big deal was the release of the SD455 engine. And, there were a few Pontiac racers that immediately got one & put it on the track. One of these guys was John Clegg. He bought one, took it to Indy, & won his D/S class !
I may have already posted this. But it needs to go right here, again.
https://www.facebook.com/NHRA/videos/2196660753953292/
I suppose one of the most famous SD455 Stockers was the Herslow & Morlock "Celluloid Hero" E/SA record holder, which made the cover of SS&DI mag.