I would suggest going easy on the cam so you don’t have to mod the Tri-Power carbs too heavily.
I know Dick Boneske runs a fairly mild cam in the Tri-Power 428s powering both his and his wife’s 1964 GTOs, something around the Summit 2802 or a tad bigger like the Crower 60243:
https://crower.com/camshafts/pontiac...amshaft-7.html
A quiet exhaust system is a big plus when you’re cruising along with the top down. Exhaust noise with convertible cars is much more apparent, you hear a lot of road and exhaust noise whether the top is up or down.