Torque Converter question

I have a 64 Barracuda with a warmed over 273 Commando engine. It's got a nice lumpy idle and the original converter is pretty darned tight. The car stiffens up when dropped in gear.
I would like a little higher stall speed but was told by TCI that since my 904 is a push button type the spline count is different than the later 904's and they don't carry anything to fit.
I'm not going to be racing but would like a little help at the stop light and a easier idle.
Any ideas?