For 1901R 4MV; Rochester Quadrajet Carburetor. Venturi(Choke tube):28mm. Manual Divorced Choke. For 1970-1972 V8 Chevy big block Mark IV 6.6L/402. For 1967-1973 V8 Chevy small block Gen I 5.7L/350. For GMC 1968-1969 V8 Chevy big block Mark IV 6.5L/396.