KX 500 pipe

Wanting to know if anyone had done a KX 500 motor in a tecate 4. It's a friends bike and runs pretty well with a 250 pipe and the exh flange is made to work with a 250 pipe. I know either a new shearer or one o the bigger honda pipes would work better. He's looking for an OOF and tring to get a old of Matt Shearer. I'm just getting ideas if anyone has any. It's ported with a (small) 40mm lectron on it right now but going bigger (48 lectron). Radar