Well, I spent this Sunday afternoon taking the radios apart and was successful in the conversion. This may be uncommon, but in case anyone needs to do this in the future with these TD-6141s with different wiring, here's how:

90' 740
female plug no. and color
-------------------------
6-yellow/white (one wire) to '87 yellow
7-green/brown (one wire) to '87 green
8-green (one wire) to '87 grey (maybe it's white)
9-black and yellow/blue (two wires) to '87 blue
10-black (one wire) to '87 black (only need one of the blacks, common)
12-red (one wire) to '87 red

orange and brown on the 87' are unused