I was wondering if it is possible too put a prox seat on a 1998 xc 700 without having too change gas tanks.

im pretty sure the tank would have to change... the tank is molded into the plastic that the cover is stapled to, so every thing from the tank to the trunk is one peace.

Yeah, my uncle had the same problem and he had to change his gas tank in order to change his seat, so he left it the way it was.