Thanks for the info. Sounds like there is a large manufacturing impact here, but what better way to judge performance than to load up 1000 backyard truck builders with a cheap R&P alternative and let them hit the street?
I took a look at
http://c10forum.com/forum/showthread.php?t=3388&page=9 and having to notch frame seems extreme. I guess the reason the MII subframes get away with R&P is that the C-arm pivot shaft is a lot shorter? Looks like the stock C-arm has a bump in the stamping in the worst spot to sneak a rack shaft through. Would tubular C-arms have helped here? What about if he had dropped the rack down below the frame, and more forward, like I think Flaming River does?
I think it has to be simple, cheap, and use available parts.