Pick a block

My 1975 360 core engine. Because I have it... Get the caps strapped along with main with studs and a 3.79 inch crank. Because with a .030 overbore, 387 c.i.d. is still plenty enough to exceed the long term horsepower limit of the block with a good set of heads. On a side note, I'm starting on a 360 LA roller short block I'm putting together for a friend on a trade. At 58,000 miles of severe truck usage, the cylinder walls still have the full crosshatch. Kissing the bores with a fine grit glaze breaker hone 10 to 20 strokes is all it will take to knap the bores in enough to seat a fresh set of rings. I don't know how either, because the crank and bearings were trashed out...
But my first choice would be an early seventies 318-3 block with its original steel crank for a 4 inch bore 333 incher. Add in some Milodon main caps with studs, H beam aftermarket rods, J.E. flat tops, and some lightly ported W2 heads.