I can't speak to the IVA requirements - but if it's in the budget and you're planning on tracking the car, I would look into Ford Racing's new BOSS block. Otherwise a Mexican block (noted by Hencho Mexico in the lifter valley)..
The Triple-X 5.0 Roller block is a little beefier than most of the other 5.0 blocks from what I've observed looking at the bottoms of the cylinder walls as they jut into the crankcase.