Three on the Tree losing 1st

The only 3 speed manual transmissions used in 1975 were the A230-side cover style and the A390-top cover style. There should be a pad on the passenger side of the transmission that will identify which type you have. Mymopar.com does not have the 1975 service manual, but there are plenty of them on eBay. Just search for 1975 Chrysler Plymouth Dodge service manual. Used 1975 manuals are dirt cheap.