Sadly, we have but one terrible picture of the mounts without the engine installed, shown below.
Here’s a drawing that looks less like a rusted mess. The engine is constrained from tumbling around the engine bay under aggressive driving, but also mounted with some concern for the reaction torque at the output. Whenever (you’re at your closed course with professional driver and) you mash the throttle to the floor, the engine is trying to rotate around the sprocket. This is because Isaac Newton decided 350 years ago that actions need to have equal and opposite reactions. If you draw concentric circles around the output sprocket (that red pointy round thing in the picture up there) any mount tangential to those circles will be in tension or compression, and any mount radially will be in bending.
For this project, the “in-bending” mounts are super short, wide and thick plates triangulated with other plates and welded to the frame. This is because (and this is a massive oversimplification, but…) “in-bending” is bad, and should be much stronger and shorter than the tension/compression mounts. Here’s a close-up of those mounts in that previous bad picture:
I did the math for these mounts; knowing the engine torque and the gear reduction, you can calculate the maximum reaction torque, then with the distance from the sprocket you can find out the force, because torque is just force times distance. Look up the strength of steel in shear (with no heat treat, because your welding will ruin that) do a little bit of math and figure out what thickness metal you need. Multiply it by 5 or so to account for the fact that things in the real world never work out as well as they do on paper (and also some mediocre welding), and Bob’s your uncle. The same was done for the other mounts to make sure they wouldn’t yield or buckle. If you’re doing a project like this, and this stuff doesn’t make sense, you’ll probably want to think about it for a bit until you get an understanding of the forces involved, and also probably make friends with someone who does.
Engines need fuel. Sadly, the S600 doesn’t have the correct pressure or flow from the stock fuel pump for the motorcycle engine because the world is a cruel, cruel place. The simple solution would seem to be to install the stock fuel pump assembly from the motorcycle into the vehicle’s fuel tank. It turns out this is not a super easy step; the fuel pump assembly is bolted onto the bottom of the fuel tank with an odd protruding oval pattern, and the whole assembly was too tall.
I just made a new tank. After designing a simple shape in CAD, the flat pattern was cut out of aluminum (CAD here can also mean Cardboard Aided Design if you’re not handy with computer design software). The aluminum piece was bent back to three dimensions and welded at the seams. If this seems a bit daunting, there’s no reason you can’t just buy a new pump and regulator with the correct pressure and install it in line from the existing fuel tank. You could also install the stock motorcycle fuel tank with pump assembly and all into the trunk. You may get some sloshing issues at low fuel level (bikes lean and cars don’t) and you might have to reconsider the overflow hose (maybe put in a loop higher than the tank and back out the bottom of the car?). In any case, make sure the tank is mounted securely and vented outside the vehicle. A custom fuel line was made with the correct banjo fittings on each end. The diameter was increased one size, as the increased length in line will reduce maximum flow and may cause issues under high load.