Once you start talking about boring your block your talking about a bunch of money. I would say rebuild the old one with stock parts and just make sure that the block and head are in good shape. I say this because the rest of the car still has a lot of miles on it but of course I don't know what it looks like. Just for everyones info. a stock motor can easily run n2o or turbo with no problems as long as it's tuned properly.