Hello all. I jumped in my 66 Tempest last night, took it for a drive and found that it wouldn't shift out of 1st gear. It's a 2 speed automatic transmission. The previous owner put a 455 from a 1970 Grand Ville in it but i'm not sure what type of trans it is. Is it a Powerglide? Anyway, it won't shift out of 1st gear. Last year i changed the transmission fluid, filter and replaced the gasket and it has been good. The level of trans fluid is a little above the mark, looks and smells good. Any thoughts on what it could be? Thanks!