What bore size is your block?
I build a lot of 400 stroker motors, only one ended up with a 4.350 bore , all the rest where bigger, 4.360,4.375 and 4.380 to get the bores straight.
I've used different head gaskets on them depending on which heads and desire compression ratio, I have used a lot of the stock Fel Pro 440 composition head gaskets on aluminum heads and pump gas.
I'll look that number up tomorrow and try to remember to add it on here, it is plenty big on the bore size