We used the Mexican Blocks with Block fill .060 over is about max
Early blocks prepped this way are good to +/- 500 HP
The beefy aftermarket stuff is way to heavy and is overkill for the HP
A4 about the Best but hard to come by
The Later Ford BOSS blocks are good for the weight but $$
I have a standard bore BOSS service block I may be willing to let go
Good Luck!