One problem I've noticed on the old Borg Warner designs and Fords follow ons is that the clutch pack stack ups may not have the correct thickness of plates when compared to the original types. his can cause friction in the released pack due to too thick steels or frictions. A person has to know the thicknesses of these items and check new parts for accuracy. I've seen questions where folks that weren't used to these old transmissions were wondering why they could't get the snap rings in the grooves since they had put it the correct amount of plates. They just didn't check them until the problem came up. Changing from the old bronze frictions to the composit frictions can be interesting, I would look for Borg Warner frictions and make sure they are at least equivalent to the OEMs.
If the car only creeps at the initial start up then will set and idle in neutral after, it may not be a big problem. After an overhaul, the bedding in process with new clutches can be interesting at times. A person just hopes that it doesn't create a problem. It may not be a bad idea to pull that pan after some miles are on it and look at what's in there. If it looks good then it should be no problem put in a new filter and use a new gasket then top the pan back up.