I'm not a big block expert, so I've little to offer in the way of help.
But if I remember right the deck height on a 366 is higher than the car motors. I presume either the rods are special length, or the wrist pin hole is at a different height.
So I'm wondering what combination of rods and pistons you are using in this motor?
Second question, if the deck height is higher, then the intake manifold is different. What intake will you be using with the 366 heads?
Maybe I don't remember correctly, and there is no deck height issue. If so, straighten me out. Otherwise, I'm curious what combination of pieces are you using?