early 700r4 used the same roller clutch as the t-350.
the late 700r4 roller clutch is wider. It also requires the matching parts to install into the t-350. You must have the correct center support from a 700r4 to set the low/reverse clutch pack clearance.
If the incorrect wider 700r4 center support is used , you can have a low/reverse clutch pack that is too tight or loose
Dont worry how old you are... it is the mileage on your body that adds up.