Can a LongTail 833 tranny be used in an A-body??

True, but then you'll also have to fabricate your own 4 speed transmission hump, as the rear mounting location will put the shifter well behind the shifter opening on an A-body 4 speed hump.

And you're still stuck with grinding down the front shifter mount and shortening the driveshaft.
Yeap true that, not that complicated i will do it in my dart, as i need to do a custom driveshaft anyways and using a V-Gate shifter!:D