keep this in mind you are in effect building a 20R engine with 22R pistons.
the crankshaft, rods, flywheel, clutch, bell housing, oil pump, water pump, radiator, starter and motor mounts all interchange between the 20R and 22R. you can even run a 22R carb (with an adapter) on the 20R intake. you will need to get rid of that extremely anemic stock 20R exhaust. if a header cant be afforded get a 22R exhaust is flows better than the 20R does IF you get the one that has the twin pipes down to the cat.
the 20R starter is a direct drive and uses more battery than the gear reduction 22R so grab a starter for a 81-84 22R
FYI with the year of truck you have and the upgrade from the 20R to the 22R check the general plugs for the wiring you are on the edge of having different plug ends. All of the plug ends were different on my 80's 20R over the 22R that was found. Had to change/cut wires and such. So check your donor and if they are different then you will need both ends of the plugs.
this is true if you swap a complete 22R engine over to your truck. BUT if building a 20/22 hybrid you will use the 20R distributor and coil
