If you have a built 340 with a stock converter, then you already have a problem, in my humble opinion. Before converting my 69 Cuda to a 4 speed, I built the 340, and kept the stock converter. It didn't like to idle, and it fell on its face from a stop until about 2000 RPM even with the 4.56 gears it came with. I picked a 2400 stall, and my car drove GREAT while it still had the automatic. I eventually switched to 3.55 gears. FIRST, I would think you'd need to get a higher stall converter. Then I would highly recommend 3.55 gears. That being said, you can not only "chirp" your tires with 3.22 gears, you can smoke them. Plus it will be better on the highway with 3.23s.
