i would really consider upgrading your clutch packs and valve body if your going to chuck a high stall tq converter on there, i have only done this with the old 727 torque flite series of transmissions so i can't comment specifically on the toyota transmissions or not, but it seems if your preloading the clutch packs to a higher stall you might want to beef them up a bit, meaning that if you trying get that low end back through the trans it has to come from somewhere like the clutch packs, the torque converter doesn't add anything to the trans it just changes when the trans does it's thing and if you think about it all of that extra energy your trying to use has to be built up somewhere then released by the torque converter.
like i said i know next to nothing about the 4runner transmissions and have only heard rumors on the 2 companies you've listed so can't be of much help, maybe just ask if you should upgrade the clutch packs and valve body when you go to get the tq converter done, all of my experience is on old muscle cars and my old 5.9l jeep i used to have.
