stall or not to all?

where do you get a factory converter like the 340 stall converter for a internal balanced 318, and a904? from what I've been reading would do well. I really want a converter that fits well 1st time, I've already put a used 1978 a904 l/up in it, and was rebuilt I was told, but it is total crap. slips and no movement before 1700-2000 rpm... literally,,, this time, the original 1973 a904 is being rebuilt b me, all the goodies going in it and a tf-2 shift kit with 5 clutch forward...and billet servos, all ready drilled rear of case for relocated vent. not doing the used thing again. all that exhaust removal will only do one more time... pain in the *** on my back!!!