where can i find a rebuild kit for my wheel horse fuel pump?

i have a early 70s wheel horse d200 with a 20 hp kholer engine and the fuel pump is acting weird. if you take the pump off and let the gravity feed the gas it over flows the pump but go a half inch above gravity the pump works fine but when i put it back together the way its suposed to be the pump acts like it aint workin at all. so can i rebuild my pump or do i have to buy a new one? if i can rebuild where can i get the kit?