Wow. 3.00 gearing is about as low as Ive heard of in a bumpside truck. Any noticeable torque issues, or dont you have many hills where you live?
As for the heating for the offenhauser intake, Im going with what most people are doing and thats radiator water plumbed through that box on the underside. Im making a plate like so
with the two spigots to clamp the hot water hose to. In and out on the way to the heater core. It supposedly provides warm water in about a minute or so to the floor of the intake plenum. Here's another view of how one guy did it. Im using this design:
Im right now making two of the plates out of aluminum.
Let me know if you decide to go this route.
Yeah Id like to see pics of your exhaust. Ive got EFI manifolds with a Y pipe (2 1/2") going into a Dynomax turbo muffler. Its OK. I paid a guy to make me a tailpipe for it but it was so crappy with crappy bends that the restriction was too much. I pulled it off and now I have nothing after my muffler.