Wheel help/Advice - 17'' or 18'' square setup on 69 Nova

[Brianstanford]

Looing to get a square setup wheels/tires for my 69 nova. Will be street, autox at least 1-2 events a month and some track events. Debating over 17 or 18 diameter.

First question- Is there a benefit of one or the other? Tire choice is more abundant in 18 but 17 has some that will work also. I can find a couple off the self wheels in 17x9.5 with the backspace (+6'') that will work, 18's not finding much. For 18's I can find a 18x9

Second question is tire size. I want to run a 275 square in 200 treadwear. Nova will have full ridetech coils F/R with Truturn, C5 disc F with camaro disc R. Would dropping down to a 255 square be that much different from a 275?

Would love to go custom like Forgeline but they aren't in the budget. Can spend $500 -/+ a wheel. Some wheels I like are the Vintage wheel works v40's, TA engineering Superlite, C5 Z06 Speedline, Rocket Racing Attack

Thanks in advance Brian