Corvairs normally run fine on regular unleaded gas at 89 octane. Brake fluid should be DOT 3 or better, if you change over to synthetic, be sure to flush the system completely . Transaxle and transmission fluids are readily available. 85W-130W or 90W are sufficient for the transaxle and manual transmissions. Dextron is recommended for the automatic transmission.
Synthetics are optional.
Corvairs that have been sitting usually pull when the brakes are applied. Wheel cylinders should be checked for leakage and operation. Disassembly, cleaning and installation of new rubber should be a bare minimum. Check for cracks and oil on the shoes. An often-missed item is proper adjustment of the parking brake.