HevyHauler, I've got the right bellhousing. It mated up to the SM420 perfectly, just like the old one did. I'm sure it's okay.
SW Radial, that's good to know the ramshorns fit. I'd like something the flows a little better than iron manifolds though. If I can modify an old set of headers to fit without mangling them, I will. But if not, I am leaning towards one of the iron header/manifolds I've seen for sale.
We now have 6 inches of snow on the ground and still falling. So until things calm down outside, I won't be crawling under the truck much. I'm glad I got the install done before winter weather finally set in though.
