I'm sure you can adapt the body if the wheel base and width are the same or very close.Welding the body to the floor of the 90 won't work and would be unsafe.Try to find another means of attaching it through fabricated brackets of some kind.Make sure you use heavy enough metal to make the brackets.That 55 body has alot more steel in it than the 90 does.You may also need to change the coil springs to carry the added weight.
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