Thank you for the reply Maniac. The problem with swapping the chassis is the registration. I had a Freightliner FL70 and DMV would not let me register it as an RV - even after I went through and added the 4 of 7 RV items they told me I needed.
They seem to be OK with the C5500 though. We are on the road now but I had my son measure the frame and it too is 34" wide. I extended the frame when I got it (the guy before me cut it off right behind the rear spring mounts) and if memory is correct I believe it is 5/16" thick so not too far off the 3/8". I'll never be exceeding 26K GVW so I'm not too concerned about twisting the frame. The heaviest load I'm going to tow is a 14K dump trailer that it is already towing around.
When I got the truck it had a single cab and a sleeper on it. We bought a crew cab and sectioned the old firewall and welded it into the crew cab so I've been down the "extensive firewall reworking" road.
My big concerns are starting with the correct engine/transmission combination. By putting something so big in the medium duty truck I'll not ever have to worry about overworking the engine. Right now it is taching 2,700 - 2,800 (pretty much balls to the wall) at 65-70 on the freeway. This little cat is not going to last very long at that speed.
As we will eventually build a motor-home on the chassis and would like to drive around the country when we retire (8 years from now) I'd like something that I don't need a CDL to drive and that will cruise up the hills at speed without me worrying about beating the crap out of the drive-train.
So the 34" is a go. Now I need to research the engine/tranny combo. I've read a bunch of posts and most of them are something to the tune of:
This engine is the best - everything else sucks.
I know that any used machinery is going to have problems and as I'm going to have to custom fab just about everything, I'm looking for the best platform to begin with. I don't mind older stuff as it usually has less wiring to contend with. Just as long as parts are easily / cheaply obtainable.
Thanks again!
Mikey