Sounds like things are actually rolling together into something tangible.
What extension housing do you have on the th350? If you want to use a stock 3rd gen driveshaft you'll need to use the 9". If you have access to a driveshaft shop then ignore me

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Just curious, why the poncho motor? You could sell it and do a homebrew junkyard wars style 350... then the trans wouldn't bolt up, hmm... nevermind, I'm just interested so keep the updates coming.
__________________
, Jon
Owner of a Red Sled.
If it\'s EFI I can tune it. Specialize in 82-95 GM (yes Lt1\'s)
\"If you can leave black marks on a straight from the time you exit a corner till the time you brake for the next turn.......Then, you have enough horsepower\" - Mark Donohue