I understand, I was thinking when you said swingarm you were talking about a dragster. I've found on all my bbc stuff in my cars that 4000-4600 launch works very well for being consistent yet fast. I think you combo would be a lot more consistent with a higher stall convertor. I now run a 6800 stall spragless and launch at 4400. If you need any other info on anything feel free to PM me.