For your consideration, I have a 5-speed Getrag 245 transmission, the popular transmission used for an e10 2002 to go from a 4-speed to 5-speed.
I drove the ‘82 320is this transmission came from for six months, and it shifted great.
It is a little dirty, and shows signs of use and wear, but with only 85K miles on it, I believe this to be a perfectly usable transmission not in need of a rebuild. I would be keeping it as a spare, but since the 320is has been converted to a M20 with a four speed, I have no immediate need for this fine transmission.
This is perfect for your E21 320i or 2002 in need a 5th gear.
Check out my other auction for a1984 Euro e24 (635csi) M30b34 big six engine...perfect for upgrading any e3, e9, e12, e28, e24 or e23!