Beefing up A500 overdrive

Spot on. The only reason for beefing up the trans for me would be to add design improvements from later models and improve reliability. If I'm already rebuilding the trans it won't cost much to add a few clutches, change to kevlar band and replace plastic pistons with billet. I just need to make sure there isn't a down side to any of this. I have already bought the Sonnax valves to allow fill in Park.