I like the idea of putting the fuel tank in the "void" area thus making the frunk ideal as a frunk ! From your photos Todd, I think I would cut out all of the glass barrier on the front of the "void". This would allow you plenty of room to re-work that part of the frame that was removed to allow the transaxle to fit in. It looks like you could bend up a couple of curved tube pieces to jump over that transaxle. They should be low and trussed and gusseted to give you maximum floor space in the rear seat area for the fuel tank. Put the radiator up front. With it tilted it really doesn't take up much room up there and certainly allows cool air to flow thru it nicely. With the fuel tank gone, there's even more room below the floor up there. Probably collision safer too ? Glass is so easy to work with and is secondary to the car frame structure. Once the frame is completed to your satisfaction, and the fuel tank is in, just replace or modify the Fglass you cut out to fit the new configuration. Same in the frunk. Fabricate a new Fglass floor to take advantage of all the room left by the fuel tank re-location.
By the way, where did you get that green elbow for your air cleaner duct work ? I like that a lot and it has a very tight radius for it's tube diameter ! What is the tube diameter anyway ? Don't know if your interested in one of these air cleaners but it is what will be on my Subaru Engine. I call it an "Air Gobbeler". There K&N filter inside is large enough to handle a V-6
