Gas block/Barrell/Fore end question

[fritzmeister]

I am going to build myself a custom upper for one of my lowers. I am looking at a bull barrel with an outside diameter of .936". I want to (obviously?) put a free float fore end on it too.

I have a basic understanding of tolerances, so my question is what is the smallest to largest i.d. gas block I can get? How many hundredths of an inch is too much?

In my short search, I have found 2 low profile gas blocks that might work, but one has in i.d. of .940" (on sale for $28/reg price $40) and the other has an i.d. of .936" (reg price of $40). Would either one be ok?

Any other suggestions...? Thanks.