TH-350 Identification

Could any of you transmission gurus help me with the following TH-350 transmission codes? Here is what I have found on the transmission. I am having trouble identifying it despite having the TH-350 Handbook by Ron Sessions.

The area where the VIN from the donor vehicle would be stamped is broken off. Here are the codes:

Converter Housing: Q1; I don’t know what this is.

Pan: B5H19D; I know that this is a Parma built transmission, built on June 19, 1975, Day shift.

Pan Rail (Front of Transmission); C1806 500 6; I don’t know what this is.

Inspection Cover Area on left side of Transmission: 15C255373 or 15C255378 (not sure about last digit). I don’t know what this is.

I am trying to find out what the original combination was for this unit, if at all possible.

I believe it was a car application, because it is a short tail TH-350.

Thank you for any help that you may be able to provide.