If you are really going to try to squeeze a few months out of it, refill it with ford ATF.

Years ago I bough a very cheap an old Dodge wagon. We used it to drag our dirt track car to the track (a couple miles from home). One day it wouldn't move. I dropped the pan, replaced the filter and adjusted the bands and by my transmission guy's advice, put the Ford fluid in it. The old wagon did the job all racing season, that last week was pretty questionable, but it got the job done. I scrapped the old wagon, the transmission wasn't its only problem.

A 1967 318 powered car with a 727 that is only street driven only needs a stock rebuild. The 1st round went 131K miles in 56 years, do you expect to put 131K more miles on it?
The only upgrade that i would consider might be the part throttle kickdown, but I think you need a newer valve body to do that.