I'm having a real tough time finding the Camaro/Firebird all over the city to use the driveshaft on my TH-350. I've checked about 6 different junkyards, and no dice. I'd like to know if there's an alternative to this driveshaft? Thanks in advance.

A short tailshaft TH350 needs a driveshaft from a 82-83 third gen that came with a metric 200 3 speed tranny. A long tailshaft TH350 can use a driveshaft from any third gen that came with a 700R4.

If you can't find the longer driveshaft, swap the tranny to a long tailshaft version to use an easily found driveshaft or have a custom driveshaft made.

It's unlikely that you'll find such a short driveshaft from any other car. Third gens only have a 101" wheelbase.

Why do most people use the short th350? Is there anything different about it from the 9" tailshaft transmissions other than output shaft length? The 9" tailshaft ones seem to be more plentiful, and they are easier to install in our cars.

The 9" tailshaft versions were usually in trucks and easier to remove.

Yes, I took mine out of a truck, but there seems to be a lot more th350 trucks than cars in jy's.
Are you suggesting that because the ones from trucks were easier to remove they were mostly already taken?

RB2, most ds's that are about 44.5" long will work, but with some you might need to find conversion u-joints. At least one of those jy's you visited must have a big pile of driveshafts, just measure from center of u-joint to center of u-joint, and find one in the pile that will work. Or crawl under a hundred different vehicles...