Unbolting 904 from 318 (anything to watch for?) Also question about rear axle (not 8 3/4)
As noted the converter bolts, the cover bolts, the starter, the dipstick tube might be under a trans to engine bolt but might not do be sure that is separated or removed. The rear trans cross member bolts and remove the rear engine mount (it's really the transmission mount but Chrysler calls it an engine mount) then all the trans to engine bolts.
When you seperated engine from the trans the torque converter may stay with the engine or it may come with the trans. It is full of fluid, like a few quarts. If it comes out of the trans fluid will be everywhere, if it stayed in the trans have a way to keep it in the trans ( preferably all the way) a piece of bent metal that presses on the torque converter and is bolted to a mounting flange hole.
Mymopar.com has free factory service manuals to download, there are procedures in each to do this job..
As for the metal thingy at the end of the tail shaft it was most likely a weight to reduce vibrations for the more luxury cars. There is mention of it in the FSM
if the rear has a cover it is either a 7-1/4, 8-1/4, 9-1/4 / Dana 60
8-3/4 has a removable center section like a Ford 9" and the back of the housing does not have a cover. It is basically round like a moon hubcap.
Also note the index hole in the back of the crank can be a few sizes, early, late, auto, manual, check the torque converter for fit prior to installation. Even if he trans is going back in the same engine