Without the proper valve body and governor parts a 727 won't last much longer than a 904. I'd be willing to bet you are having to manually shift the 1-2 shift, which is hard on any trans with a stock v/body. The nose over, or overlap from the low/reverse band being applied and not releasing before the kickdown (2 nd gear) band applies is where the damage occurs - in effect it is in 2 gears at once.

My advice is after the kickdown band is adjusted is to either install a manual v/body, or a good shift kit to make the trans shift correctly, and use the governor to adjust the shift RPM's.