Placing a truck on the roof

[customstepvan]

I hope I am still welcome here as I need some help with my RV. I don't have my minibus anymore and did not buy a replacement stepvan as planned because even the pieces of junk of these vans can be expensive. I only want to have a rolling luxurious bedroom without bathroom, kitchen, etc. for overnighters in RV parks . I have seen the pictures here of the VW type vans "glued" to the top of the bus with (presumably) the underlying top of the bus cut out forming a "huge skylight" and raised roof type of application. I bought a 1977 Ford Ambulance type vehicle and am going to gut it and weld a matching sectioned cargo van on top to accomplish the higher ceiling and the skylight effect. I have seen the pictures of this done here but cannot find a thread on the pitfalls and/or how to actually do it. Can someone lead me in that direction? I know I can figure it out for myself, but I don't want to make the usual "new project" unforgivable errors.

[customstepvan]

Actually I just discovered the perfect rooftop application would be the very long and high 8' Pickup Camper Bed Topper for the "raised roof". Used ones are cheap, waterproof, already have good windows of various designs and because the rears are usually slanted you can turn them around to be more aerodynamic at the top of the front to save gas and place a small window a/c unit in the more upright front end of it now located at the back of the top of the truck. Maybe even mold two together to size perfectly. Anyone have any tips on how to attach for water proofing?

[bbkid]

well, i have seen more than my fair share of conversions done, with vw's especially. the most common method was right angle brackets attached to the roof beams. most people welded sections, almost like a long tack weld, to add strength. then they sealed it with caulk. i've also seen a couple welded all the way around the seam. another thing i've seen for extra sealing is the use of trailer roof sealant around the seam.

note: i don't personally vouch for the strength of the attachment methods used by others. i'm just describing what i've seen.