OK, for '63, Pontiac still had the 421SD engine plus "Swiss Cheese" frames, & other lightweight parts.
Also had the 421SD powered '63 Tempest/Lemans A/FX cars. One of these again won A/FX @ the Winter Nats.
Some of these cars eventually ran in the "Modified Production", Gas, & other classes.
Jim Wangers won the B/FX class @ Indy, in a 421SD Cat.
Some big cars again ran in some of the other Top Stock classes.
And, there were '63 big Pontiacs that ran lower classes.
It was the last year of major factory support, & the last year of the 421SD. I see it as a sort of end of Pontiac's "Glory Days". The factory supported Mopars & Fords took over. Most of the top Pontiac racers switched brands.
For the next 10 years or so, it would be mostly up to independent & dealer sponsored Pontiac racers to do the drag racing.