Hi guys, sorry not been on for long time.
Yes Bulletcars is only place now that has manifold but the casting isn't as thick as a richwood who's design was for drag racing (think first customer was piranha racing using 6ltr psi blower).
You are right with a couple of things Zuffen with the porting, intercooler an cost an your running a smaller blower than I have (3. 3ltr Whipple, non intercooled, twin 3" throttles with 16-38psi cost $14k) but it cost around the same for a harrop ls blower set up with less boost. Yes a twin turbo set up would cost $3-5k an provide eazy 25+psi.
I spent about the same as you did doing custom billet cams, rods, pistons, head mods an port matching, blower set up, fuel system an ecu but my set up was built for 40psi@10, 000rpm