Do heads have to be on to pull a block?

It shouldn't matter either way. I think the preferred method is probably to do it with the heads installed, so you don't run the risk of damaging the deck in any way. If you already pulled the heads, just use the headbolts through a chain to pull it.
 
my car was stripped to the block when i pulled it. i just used the bolt holes where the head bolts go to connect the chain.

corona.jpg


joe.jpg