Some of the F750 FIRE engines seem to be running the split Webers that lots of mini racers used on very long induction manifolds.
But, for ultimate cheapness (given that emissions don't matter) why not a 48mm Dell'Orto TB (£30 or less in a scrapyard near you) mated to an MPI head?
While I'll cheerfully accept that a carb will give as much power as injection, EFI will always give better throttle response and driveability (when properly set up).