Crank Bearing And Oil Pump Question

i'm replacing the crank on an unknown hours rebuilt oem crank with a falicon rod that the rod bearing went bad on. it was supposed to be low hours but i think the guy was full of w00ter. it has the oil mod. the main bearings feel tight and good but i'm not sure if they were replaced when they put in the rebuilt crank. do the main bearings usually go bad or just the rod bearings? also, what parts of the 07 oil pump do i need to buy to do the oil pump upgrade, the bike is an 04.