Ok. Definetly use 15 springs then and don't go crazy drilling out the hole in the spacer plate that's for the 2-3 shift if your using a kit like a Trans-go that has you drill out the spacer plate. Otherwise you may have shift overlap. I can understand not wanting to trash the converter but by the looks of it there may be a sealing problem and/or problem where the bushing isn't tight and lets the converter walk around. If it were me I'd send it back to the mfg. and see if they can replace the snout and flush it. That'd be a lot cheaper than buying a new converter and will ensure you don't put it in and trash your new transmission.
BTW: if you do a torqueflite again don't use the 5.0 lever. It is designed for the wider/stiffer solid front band that a Hemi trans. uses and is a little too stout for the narrower std. band. It works but sometimes you get shift overlap. Generally if you use 15 springs and don't go crazy drilling the transfer plate your ok but even some will overlap when you've done that. I quit using the 5.0 levers because of that. Now I only use a 4.2 lever and the 2-3 shift is always crisp yet smooth. Just my findings.