ROCKLAND Std Gear makes a T56 conversion. Never used it, know nothing about it. Someone else (Transdapt, Novak or Advance Adapters) makes a kit to convert a Muncie 4spd to 4WD use. This involves changing out the mainshaft on the Muncie. Otherwise your choices are T5 (too weak) SM465 (3spd and not suited for hotrodding) and a few others. Im a stick guy and I'll slap myself for this but you're probably better off going with a 4L60e 4 speed Automatic.
The problem with converting a non 4wd stickshift to a 4wd stickshift is the short-run, low availability and unknown quality and lifespan of the non-oem mainshaft necessary to make it work. The OD automatic covers a lot of your trouble areas; its readily accessable, easily serviceable and a common swap. They can also be easily built to handle the LS power with a long service life. Just make sure to use a fluid cooler and a quality ATF in the proper quantity