Well, it looks like you've got two pretty solid machines there; it shouldn't be too much work to make a good running bike between them, and the CL exhaust pipes alone are worth nearly what you have in the two bikes combined, even in not-so-great condition, so I say you are WAY ahead on this project already! You just need the time and elbow grease.
The Honda 450's had something near 50+ HP stock, and I know mine rode really well, even at highway speeds, I never felt underpowered; passing at 80mph never worried me, and that's saying a LOT for a 30 year old 450! I think you have a whole lot more bike on your hands than all the old 350's and 360's running around; even if you just get it going and sell it to finance your 750 project...
Good Luck mate!