This bike im working on is a vt700. My title says vt700, my engine says 694cc, wikipedia says this:
In 1986, The "VT700C" model rear fender took on a flair look over the rounded style. The engine is the same as the 1984 model except polished instead of black with the right engine cover graphic painted black. The mufflers were a little lower and changed from the flair look to a more straight style. The front pegs and controls were moved forward, the rear foot peg support bracket became solid and the back rest was optional this year. The cast wheels changed from a ten-spoke to a five-spoke design and the access covers were chromed. The "VT750C" was available outside of the USA (Canada and Europe) with a larger engine displacement.
The 1987 "VT700C" model featured the same engine as the 1986 model but with the right engine cover graphic not painted. The side covers are chrome, five-spoke cast wheels with a single front disc brake.
The VT800C was only made one year, 1988, after the tariff was lifted. It had spoke wheels, not sure what else because i haven't looked but i thought pretty much everything else was the same as the 86-87 VT700c's
The frame/airbox issue can be fixed by cutting the back bone out and making a new one. You could then use velocity stacks or what ever you wanted for an intake or a fuel tank. It would also give you more fuel in the tank depending on tank choice.
Here is a picture of a vt800 (yes, the rear spoke wheel will fit i've read..) everything is basically the same as the 86-87 vt700c.
But yeah NOOB ;) , if you have any questions or anything i can help. So, do you have a vt700 or a vt800? Either way, they should be exactly the same.