If it's a case of either being okay for your budget, then go for the 32' by 65.' If you do a full back straight into a sweeper, that's a decent high speed section. And assuming 8' lanes, the remaining 24' of depth translates into an infield three lanes deep, which is just fine for your twisties.

We run a non-profit track out here in Seattle, and it's going great. Good luck.