M1 Single Plane Question

I have been playing around with my combo and have noticed something very disturbing. My M1 Single Plane is a spreadbore design. I'm running a QF 950 DP on my Eddy headed 408. I've been playing around with spacers as well. Don't know why I didn't pay any attention before, but dam it seems like a bad mismatch between the spreadbore intake and a square spacer. Am I missing something here? Trying to improve 60 ft. times and it looks like a poor air/fuel flow match between the manifold, spacer and carb. Is there a different M1 with a square bore carb flange that I need? Thanks for listening.

Darren