Bought a complete bottom end...how would I clean the block since I don't have a head yet. Or is it best to wait till I have a head on to clean it?

 

wait till you get the head, why run the risk of getting a bunch of crap in your motor? if you decide to do it anyway, use some masking tape and tape off the exposed part of your block, and if you use power tools to do the job be REALLY careful not to hit your gasket mating surface.

 

heavy duty 5 horse vacuum...lol clean that **** up!!