ive looked at the olds engine before you can build a cheeap stroker with buick rods and pistons and countergrind a olds crank. supposed to be good for motorhomes
i am not shure about the best stock heads but i will do some checking a really good site is the(olds faq) site tons of info re what to use.
i had a 72 olds 88 with a 455 about 10 years ago and it was the nastyst big 2 dr boat i had ever driven . a true 140 mph car till it finally let go.