[olddog]

If you go with an aftermarket block, the 4.000" and 4.125" bore is the same price. Definitely get the bigger bore, it let's the valves flow more air when they are not as close to the cylinder walls.

Also, I would look at going to the 351C main bearing diameter. Definitely if you want to turn the rpm up. Maybe not if you are going max stroke and plan on keeping the rpm down.

I'm not real fond of the rod ratio when the stroke goes much over 4.0", but I haven't heard anyone claim they are prone to failure. Bent - where would you limit the rpm on these longer strokes?

The last block I had done (Chevy), I could have had a new block for about the same money. Chevy is $1000 cheaper than a Ford and as Brent said you still need to do some machining, but the aftermarket blocks are much stronger and better oiling. You don't need all the girdles, which are not cheap either. No doubt a factory block will work and it is cheaper, but the aftermarket is very tempting, especially with the 1/8" bigger bore.