Wow!
That was (or IS) depending on your point of view - my current pop-up camper!
I have a 1973 Starcraft Starmaster 6 I've been refurbishing for the past couple of years (very slowly, as time and $ allow)
It was kinda weird seeing what appeared to be 'my camper' demolished

but you're doing such a great job that I got over it quickly!
I LOVE the plastic corners on the roof! that is a huge issue for old Pop-up owners like me, as many of those old starcrafts have rotted roof boards and need total rebuilds. Where did you get the plastic material to make the corners? is it available commercially? was it already in an 'L' shaped bar of material? or did you start with flat plastic and have to form that corner, too?
How are you planning to seal the top to the bottom, so it doesn't leak, esp on the road? just rubber weatherstripping? or are you going to re-use any of the channel / alum from the original camper?
As for the walls - why can't you just make them canvas? they are actually making some Pop-ups now with only ONE bunk end, and the other end is a flat wall of canvas/window - just like the sidewalls. While the original canvas may not be salvegable , you may be able to use it as a start for a pattern to just make four straight walls. The original corner Zippers might be useable - they are pretty tough, unless someone let them rust. The special track that holds the canvas up on the inside of the original roof is probably ok to re-use, and a decent boat cover/canvas repair place, or one of the known pop-up canvas replacement shops should be able to make you new canvas to fit.
I have heard some good feedback from this company - though I haven't used them personally.....
http://www.canvasreplacements.com/our_history.php
For the person who asked about the lift system - I have a detailed, manual of the original lift system for 1982 and older vintage starcrafts like this one. The manual is about 16 (?) pages & has detailed instructions and diagrams of everything. I have owned two of these 70's PUP's, and this type of lift system ( Called the Goshen system) is the easiest I've seen to maintain and repair. If anyone would like a copy of the manual (in adobe acrobat format) please e-mail me at LauraT7 at SBCglobal dot net - I'd be happy to share it with anyone who is working on one.
Laura