I have a 68 302 block punched .30 over and am wondering if I can use the block on my 89 5.0 motor and if so what mods are needed.

 

you have two blocks and you want to use both?? im confused by your question.

the parts are interchangable if thats what your asking. the 68 block wont be a roller block so you will either need to have the valley drilled and tapped for the spider or you will need to run special lifters.

 

You'd be better off machining your existing 5.0 block, honestly. The older block will fit, but, as mentioned, you won't have a roller cam. In addition, you'll have to buy new push rods and most likely an adjustable valve train to compensate for the minor block and head height variations.