The fp housing is more like a .68 a/r IIRC. The fp housing comes standard for the smaller exhaust wheel of the 3052 and 3065 and is machined to fit the normal 3582 exhaust wheel. Also you said you had the same setup as dave b. but he was on a t3 82a/r and custom header. Now he’s on another custom header and tial 82a/r. Not to put you down but the fp housing and that cast manifold will never make the same power as a larger housing and custom header.
I hope you don’t take this the wrong way, I’m just stating facts.
The cast manifold will probably hold up better/longer though.