[MAStuart]

You need to post a picture of the heads. That will tell in an instant if they are in fact 289 HiPo heads. Early heads had the guide plates built into the heads. If they added guide plates without machining the cast in guides out that is a no no. Did you have them crack checked? How do you know they were milled a bunch? Did you CC the chambers? The casting number and date casting numbers will tell you what the block is. But to really tell what it is you need to at least pull the pan off. This is if you think its a HiPo block . How many bolts hold the bellhousing on 5 or 6? What size are the rod bolt nuts? Does it have wide main bearing caps? This is the kind of stuff that helps to find out what you got.