first off, thank god someone knows how to type out logical sentences. you are now my new best friend.
now, where are the heads cracked? if they are cracked between the valve seats then it is normal and your car will run fine even with those cracks so long as they arent big enough to leak coolant through. the block, however, is nearly indestructible so long as you didnt let enough coolant run around the crank area to screw up your bearings.
as much as i hate to tell you this, try the new heads on the old block first before you make any assumptions or pour any money into the block.
