rear end conundrum

[Steve barham]

Hello, everyone. I am rebuilding (from chassis) a '74 dodge sportsman brougham coach. I have put in New sub floor and have carriage bolted the base plate. I am eager to start framing, however, the elephant in the room is begging for attention. Behind the leaf springs the cargo van chassis ends and the (bolt on) RV extension is added. There is almost a 2 " drop from the van chassis to the back of the frame. The double pivot leaf spring design makes me think this is intentional. Does anyone have experience with this? Should I just jacked it up from the rear and frame it level? Should I frame it level by welding forged Steel shims? Any experience shared will be appreciated.

[Rich Thomas]

Hi Steve, I don't have a dodge but my G-30 GMC chassis is built pretty much the same in relation to the frame extensions ( Bolted on ). I will be up at the garage tomorrow and i'll crawl under and see if I can give you some insight. The only draw back is my sub floor is covered with sheet aluminum and it my keep me from seeing whats there but I will give it a shot none the less. 

[Steve barham]

I'd really appreciate the insight, Rich.
I'm thinking this must be intentional. Probably leaning towards jacking the rear up for the framing process and then slowly lowering the Jack as I pray for a positive outcome.

[Rich Thomas]

Hi Steve, I took a look at my RV and the extension rails are flush with the frame rails no drop down. I took pictures but I can't get them to up load to my computer. I up graded to windows 10 and can't get it to my phone pic. files.

[Steve barham]

Hmm. What year is your GMC?

[Rich Thomas]

My Travelcraft is a 78 on a 77 GMC G-30 chassis and I figured out my phone to computer link and here is are the pics