Torq converters
No a torque converter from a 727 won't fit a 904 and viceversa. But not only was there a change in input splines on both the 727 and 904 in the late 60's if you have a 273 you have to make sure and get a torque converter that will fit it. The 273 was an oddball and had a smaller pilot hole in the crank where the tc slips into. Recently a buddy of mine couldn't locate a tc for his 273 and ended up taking the crank out and having the pilot hole machined out to accept the bigger tc pilot. He thought about having the tc machined down but every tc shop told him there wasn't enough meat there to do that.
Most likely the late 80's would have been a 727 but nothing is written in stone when it comes to Mopars. You'll just have to take a look at it. Watch also that a trans. from that year isn't a lockup type. If it is you'll have to run a switch for the lockup function. If you change from a 727 to a 904 or viceversa you do have to change the driveshaft length and yoke.
I have only ever seen one torque converter cracked and leaking and that was on a forklift. Maybe I am just lucky but never seen one leak on a car. When you pull it you can take it to a trans. shop and have them pressure test it.