I've got two '90 truck 4 bolt main blocks that are cast Hi-Perf. And as far as I know are one of the strongest blocks that GM made and will go to .125 over and still be safe, if needed....But are not fact. roller. ti-bar retro roller lifters are not really that expensive any more.
In fact we've made over 700 rwhp with a F1r with these blocks(w/iron heads even) and built several nitrous motors making over 1k spraying....
