Bell housing question

[bobdylan]

I have a truck that has the sm318 3sp. I am thinking obout changing to sm420, is it a different bell housing? And will I need to change drive shaft. I quess I would need taller transmitton hump? Bob

[Funky61]

From the Jolly Site;

http://6066gmcguy.com/3-to-4-speed.html

[bobdylan]

Thanks for the link