Dwayne is giving you good advice , I'll add one thing I learned ...

Put them BOTH on a block before you do anything , make sure they drop on the dowel pins AND that you can get ALL the head bolts in. I had a set of the 383/440 street castings ... Stage 6 core based ... one head was ok , the other head dropped on the dowel pins and only 2 head bolts would go in, the dowel pin holes were drilled at an angle.