Where did you get the 1.75" primary/port info. The 32's, 320's, 430's and 500's are 1.5" ports. I do not know for the 55's, sc or not. 1.75" is too big for primaries on the V6's based on every bit of research I've done unless they are only ~20" long each which would help power up top on the rev range but that isn't where I would focus to build power if it were me.

The M113's (V8's) aren't even spaced firing, yet 55K guys still pull massive power from headers.

It's just a matter of the right engineering for construction, material, and the one thing I was bashed on that I now agree with is space constraint. With how many bends that would have to go into each primary to pull off fit, it would be extremely hard to make it smooth flowing enough to really pull good power. I have an idea to get around this but we'll lose ground clearance.