head gasket help please!!!

i have a 93 b2200 i think it has a b2000 bottom end and a b2200 top end. my problem is when i fill my radiator full my truck runs rough and smokes until it gets about half full then it runs fine no lack of power the fluides are all staying where they belong. the reason i think it is a b2000 is because the oil filter is one from a b2000 and the dizzy is from a b2200 (bought a new cap and rotor). what could this be cracked head,block, head gasket?? by they way i also have a 87 b2000 and this 93 b2200 which i plan on bagging shaveing everything the 93 in static dropped with a toyota front bumper the 87 was getting this treatment till this on came along i'm going to be selling the 87 later it needs a head (cracked head) but body is in decent shape later KRIS

Blown head gasket.It is letting water into your combustion chamber until the water level gets so low the pump will no longer circulate it high enough to get into head area. You are going to fry a head if u havent done so already.BJ