The three best 904 family transmissions to start with are these part numbers. 3681844, 4028465, 4028878. These are all non lockup and have the five clutch front drum as long as someone hasn't changed the parts with another trans.
I am currently looking for a center hood trim and plain front bumper for said 1978 Aspen. I have a 1977 Aspen and also a good grille for a 1978 so I want to change my front end into a 1978 model.
Plain front bumper=no nerf strip and no guards.
I weighed my car on the scale at the drag race track. At the time it had a full tank of gas, an 8 3/4" rear axle, a 340 with a 904 with T-tops and the extra metal that came with that option, air conditioning, speed control, twin outside rear view mirrors and it came in exactly at 3900 pounds...
At this time it hasn't been up for a while. I don't know if it is finally hosed or it will rise from the dead. We will see. I wish I would have saved some of the things that had been posted but hindsight is 20-20.