I'd bet that you'd be way ahead sticking with the FJ40 frame & just swapping everything over to it. You already have the motor mounts for the V8, so sounds like T case cross member for the TH400, relocating rear spring pads on rear axle to mount SOA to stock or reversed FJ40 springs, out board the '40's front spring hangers, drive shafts, & Saginaw cross over high steer / steering column. Part the rest out, what doesn't sell, call up a wrecker to take to the scrap yard