You hit the nail there, getting a converter for a 350/400 is vastly quicker/cheaper, please notice that I never included better.
The 350/400 converter market is flooded with possibilities to experiment with different stall speed configurations when cash is limited, but you are unlikely to find one that will last under the stress of a competitive turbo V6, face the facts that anyone preloading an engine against a converter to build "Boost" is seriously damaging their own pocketbook, if you can "load" and go spending less than 5 seconds against a converter before launch, you are way ahead of the game.
Spending more time than that just trying to build boost is more like frying your transmission under an open flame, but many probably do exactly this and expect them to live,....ain't gonna happen kids, at least not for very long.
Boost = torque,......learn to know how much torque you need for the launch of your desire, then build from there.
I will call you a fool if you think you need more than 15 lbs boost to launch a Turbo Regal using a 200-4R with 3.42's and not have the front wheels dangling, anymore is pure photoshop glory.
If you can't spool to 15 lbs in the count of three battleships, you've got issues under the hood:exhaust leaks pre-turbo, horribly tuned, or just way tooo big of a turbo for intended usage, ie: 8/9 second squeezebox on top of a stock long block.
Pure stock engine/turbos/converters have been known to go "wheels up" using nothing more than a transbrake and slicks(and some kind of engine restraint)
There is something for everyone when it comes to converters, just don't be stupid asking it to do something that it really shouldn't.
This converter overheating is what cause's most transmission problems, bar none.
Kevin.
