get a galv chassis or a old chassis, repair it and have it galved
just done a camel trophy one, cost 300 quid to be shot blasted and galved.
ive just given my old chassis from my 90 away foc !
only took me 20 hours to change the chassis over
:P
however thats in a kitted out workshop with 4post ramp ect ect, so cheating in a way
if you were to build a 100 inch, its dead simple, but make sure you use everything from the 90.
afink it equated to just enough points to retain the origional reg, but personally i'd q plate it for absolutely no comebacks in the future
dan