Best for what purpose?
Adding CFM to a truck will only help at engine speeds you don't want to use.
You can't buy anything like a QJ bolt-on, the Sprint model bought new is $$$, there is no manifold, results are entirely the work of someone with experience and fabrication skills. The common QJ to Holley pattern adapters are notorious for bad vacuum sealing.
Some original Sprint QuadraJet carburetor numbers are 7026260, 7026261, 7041314, 7041315, 7027260, 7037260, 7027261, 7037261, 7027268, 7037268, 7027269, 7037269, 7028260, 7028261, 7029260, 7029261
The 390 is popular because it's available and it's been done. Clifford suggests an “85” (8.5) power valve and a .048” main jet as a starting point
Last edited by panic; 03/10/2022 11:53 PM.
