[theastronaut]

If you currently have a 230/250/292 and you're planning on adding a small block later, the only trans I'd look into would be a '94-'97 LT1 F-body T56. All the components needed to adapt them to a inline six would work to adapt to a small block, so you'd only be buying parts once. You'd want no lower (numerically) than 4.10 gears (4.56 if you have taller tires) to make use of sixth gear. With a 29" tall tire and 4.56 gears, you'd be doing 2000 rpm at 76 mph. They're rated at 450 lb/ft so you won't tear it up either.