carb choice??

I think you may have ended up with an engine quite well suited to alcohol/E-85. Since you haven't bought a carb yet, I would suggest a 4150HP set up for alcohol then jet down to run E-85. E-85 is 105 octane and is way cheaper than race fuel. You'll make more power and run cooler plus it's easier on parts. Availibility maybe the only problem in your area, wherever that may be.

Just food for thought.

PS:

Some machinists will do exactly what tell them to do with the assumption that the customer knows exactly what they want. Some are very dilligent and will call and say "Are you sure you want to do this because (fill in the blank here)". It's a good idea to let them know what the intended purpose of the engine is and do your homework before bringing the block to them. Also, get a copy of the work order when you drop the block off and read it. Call them right away if something doesn't seem right. Machining involves removing metal and when it's gone, it's gone.