You might be better off finding somebody that fully understands chassis geometry to do the designing and then locate a top notch welder to put it together.
Failing that look to altering the track and wheelbase of an existing (proven)design.
Have a look on here: http://jawfish.proboards43.com/
or do a search for Terrapin racing cars
I built one years ago, very helpful people including Alan Staniforth the original designer.
If your after doing it on the cheap, which I assume you are since your posting on mig-welding.co.uk, haunt of the diy'ers, instead of putting a advert in one of the various racecar construction magazines etc, you most cost effective way to develop a well handling safe chassis would be to select a kitcar suitably equipped with said spaceframe and a similar engine package location/wheelbase etc and clothe their chassis with your shells. If you sold in any numbers, Im sure they'd be willing to alter the chassis / supply at a reduced price etc. Of course it wouldnt be very bespoke then would it?
You could always ring up robinson race cars or similar and pay them to do the job properly.