If its a 4 spd. the floor should be a high hump with a removable section of the floor .If so the trans. can be installed with someone guiding the trans. through the hole in the floor and someone lifting the trans. with a floor jack from below. Although my trans. is a lighter t 5 I've done this a number of times with just the help of one person in the truck lifting with a rope around the trans. and me guiding it into place from below. You might also consider a 4x4 running across from one door to the other and a chain fall lifting the trans. with the heavier trans.

John

good planning is no substitute for dumb luck