First off, it'll help for you to know that the MKII Celica Supra used a 5MGE. I believe early model Toyota Cressidas also used this engine. Unless you're dead set on the 5M, I'd find a 7MGE or 7MGTE. More power potential, hell of alot easier to find aftermarket parts.
935 Motorsports in CA carries parts for the MKII.
935 Motorsports Home Page