Interesting question. You don't see the old tranny used very often with an LS.
The LS motor has a small extension on the end of the crank that may be a problem.
I haven't checked but you might need an equal depth spacer to make that tranny work because of that minor crank protrusion.
I'm not sure how that will play into engagement depth of the convertor but it's worth checking into. Personally I would probably call someone like TCI Transmissions or check their website.
There might be a nugget in here for you as well.
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