I have a mild street and strip car small block I was thinking 391s I’m running a 26 inch drag radial However that may change with the mini tub

3.91s in mt 65 with built 440.Did run 4.88s on the street.The 91s run decent with 27 inch tire.Mine is radical and not enough gear for it.Ill probally go 4.30s.Rocky

More info needed. How mild is your mild engine(mild is subjective, tell us what you've got) and is that likely to change? How heavy is the car? What size tire after minitub? Mostly street or strip? Do you expect to drive for any distance on hiways and keep up with 75mph traffic or strictly local shows or cruises?

72 360 stock bottom end with 268ex cam Heads J head only clean up with 2.02 v Heads have been decked 40,000s weiand 8022 intake 650 holley dp Doug Thorley headers 1/3/4 MSD 6 AL.100 of nitrous 69 Dart maybe 3000 pounds I would say 29. Right now the car has an 8 1/4 in it and I’m switching it out to a narrow 83/4 Standard mini tub splitting my original tubs going to the frame rail
No driving on the freeway local car shows and cruise nights

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If it was mine it would get a 4.10 or 4.30. Probably 4.30. Only 5% difference. Next would be a bigger cam. As we used to say, "more cam, more gear, more tire"

4:10 with 27 inch tire.
OK for short highway hops at near 3,000 rpm

69 -6bbl car replaced 4.10 with 3.54 then 4th gear over drive. now i can drive on interstate without getting run over.