Beamin23

What's the highest stall converter I can run on stock 70 cutlass 455 with a th350 stock gears just with j heads and 750 carb and long tube headers I'm planning on getting a 3.42 and later down the line

svnt442

"Stock" gears can be anything from a 2.56 to a 3.91.
Also what do you have it in? The weight of the car will make a difference in how the converter reacts.
I had a 455 that I did a basic rebuild on with J heads. All I did was use L2323-30 pistons and an Erson JB100 cam. I had this in a 70 Cutlass post coupe with a TH400 trans, a 2.56 gear and 255/60/15 tires. I used a B&M holeshot converter (advertised as a 2500 stall) and had good success with it.
It all depends on a whole host of variables as to what will work for your combo.

Fun71

What do you mean by "stock 70 cutlass 455 with J heads"? Is the engine an unmodified
73-76 455?

Converter RPM should be matched to engine, cam, rear gears, vehicle weight, and intended usage. You gave most of that info, but what is your intended usage? Street cruising, drag strip, or ???

Beamin23

the block 396021 F not FA on the block I don't know why it has j heads it was in a 77 cutlass I have long tube headers performer intake 750 carb stock cam and 2.56 and it a 72 cutlass convertible no a/c on 15 inch wheels and it going to be a street car