Engine Mounting

[BusaTransplant]

I think someone already mentioned it before, but maybe make the stock GS tank a dummy, and mount a fuel cell under the seat.
You could cut the top of the frame and the bottom of the tank out, and the tank would basically be a shell with no bottom, and room for the tb's.

Unfortunately I think the assembled TB’s are wider than the tank.

 

[sixpack577]

Unfortunately I think the assembled TB’s are wider than the tank.

Let the tank edge drop between each 2 outer tb's.
I think you're going to have to get really creative with the fabrication to pull it off...but it can be done!

 

[sixpack577]

Or cut the tank
Make it wider and less deep.
Which could possibly hold the same or at least a decent amount of fuel, if you choose to keep using it as the gas tank vs just looks.