I took some more photos today to illustrate exactly what I'm dealing with..... as I said before the main bus frame only goes to the rear seat. At that point two frame members are bolted onto the outside of the main frame rails, which then curve downward about 8 to 12 inches then level back out and go to the rear bumper.
I also found quite a bit more rust that I'm gonna have to deal with, but fortunately it doesn't look TOO bad, again just surface rust that will have to have a wire wheel taken to it then repainted with Rustoleum or similar.
#1 - taken from curb side underneath.
#2 - taken from drivers side through air cleaner side panel opening. You can see the main bus frame where the subframe starts the downward bend.
#3 - taken from rear, on curb side, looking between radiator fan and engine. The fan is blurry because the engine was running when I took this picture.
After the closer look I got of it today, it does seem to be a more sturdy construction than I first thought, but I would still prefer it to be one full-length piece rather than two bolted together. But it is what it is and I'll just have to work within those limitations.
I wish I definitively knew what the tongue weight of a tandem dolly loaded with car and bike would be, within a few lbs.... or if I opted for a flatbed trailer long enough for both, what that would be (more than the dolly if the trailer axles are centered, I know...)