Do you have a spare frame, or the back half of one?
You could cut two apart and put them back together as one longer one with only one weld joint. Make the front section of the frame as long as possible.

If you need a new section of frame made these folks can do it, and fully understand how and why, might even give you some suggestions or pointers.
I got a quote from them to form some 4" channel and some crossmembers that I'll make into a sub-frame for my goose neck hitch.
http://www.pgadams.com:80/

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-