(assuming crank is in top condition)use a neoprene lip seal at rear main seal. ensure the little pin in main cap that held rope style seal in place is removed and seal the little hole left by it. fit neoprene seal with lip facing in to sump and fit it staggered in the block/cap by about 1/4" in direction of engine rotation. lube the seal well or it will burn on fisrt start. apply small ammount of gasket sealer to block/cap mating face and torque to spec. now! fit rubber strip seals between sides of block and cap, first put a dab of rtv sealer on end of strip, measure strips and block depths to ensure strips are in all the way. now fit steel pins between block and strip and trim off any excess rubber. now your rear main wont leak. also, check all the gallery plugs and cam plug in back of block to ensuse no leaks there either.