my 74 auto works good, from what I can tell they are pretty reliable, but I'm sure there are problems to be had... it is easier with an auto to get the motor in and out and it is "fun" to get to the torque converter bolts through the tiny window on the block...
When I first started messing with mine, I though I had problems with the transmission since it shifted at very high rpm's and didnt go into 3rd, but I later found out that was just because the vacuum line had come off that goes between the motor and transmission.
The only issue I have with mine now is that it leaks a little transmission fluid around the pan gasket. Otherwise it works great!