Actually a GP30 or a Life Like GP18/20 chassis would already be set up for the low short hood as well. Probably not an issue to swap trucks out, I believe all three would match the truck centers and frame length... I could be wrong on that though.
I have taken the sideframes from an Atlas RS1 (china version) and have put them on to Atlas/Kato GP30/35s and (china) GP7/9 and they work just fine. No if some one would do a correct 1st gen FT F3/7/9 & GP7/9 truck to fit Atlas or Kato Trucks would be great.
If you are game to send the dog house to me that would make it a much quicker turn around and I can do it almost straight away, if you are happy to send it to the UK PM me and I will give you my address. Cheers, -James