This is a no brainer. 800 cfm Thermoquad, 6000 series, which is what came on the car originally. Plenty available on Ebay that just need a clean up & overhaul kit. You could also contact Woodruff Carburetors, one of the sponsors on this forum. A mate recently bought a pair of Competition Series TQs [ rare ] from them & they were reasonably priced & arrived as described.