I'm looking at buying a 71 D100 pickup with a 318 and 3 speed on the floor. I'd like to know if my extra 23 spline 833 4 speed will replace the 3 speed easily. Are the trannys the same length, output splines the same, trans mount, etc. Is this a direct bolt in or will I have to do some mods? Also, does anyone know anything about rebuilding the manual steering box on these trucks?

You'll need the 4 spd bell to install a 4 gear,....I have several 70/71 D100 and Power Wagons,....the manual box is best replaced with the Flaming River fast ratio manual box, they have an application just for the early Sweptlines...about $400+ last I recall

The bell housing on my car was from a 3spd and 4spd bolted right up just need another yoke the 3spd is different

At some point, Chrysler commonized the bellhousings. Before that there were different bells for 3 and 4 speed setups. A rough guide is if it's iron it's not commonized, if it's aluminum it is, but I do not know if that holds true for trucks.

However, if you pull the trans and there are two different bolt patterns drilled in the bell for a trans to fit, then it's commonized.