Laneco got me looking at thunder ranch, and they have their tube frames for the 550 kits
Something like that would be cool, if you could transfer 914 components directly onto it.
As for making a custom tube frame, I saw a neat trick on a build diary for a Bonneville streamliner:
They make a complete frame out of 2" PVC pipe, using heat lamps & torches to make the bends. Then, once the whole thing is mocked up, they disassemble it and use the individual pieces as templates for the steel tubing.
Neat stuff, and it saves them building it out of steel only to find they can't fit in it with their helmet on