Mdeardoff, I just acquired a 34 year old Hi Lo that I knew was going to be a rebuild. I too, found the steel in really bad shape. I'll be replacing the bad stuff with 1 x 2" (free) and also installing gussets at each intersection. Time consuming, but longer lasting. The 1 x 2 allows for better purchase for the panels. Whatever happens to this unit after I'm finished, it'll be better than new, for sure.
Best of luck with yours, your in the right place for assistance.
2703 Tow Lite
Bonita Springs, Fl. &