A vintge 39T sprocket does not exist, as best I know.
Suntour offered a 14-38 five speed freewheel, but you will need a RD that can handle the big sprocket. Suntour three pulley model RDs and Sachs Huret Eco Duopar RD will work. Possibly a few other Suntour RD models.
Welcome to BF and C&V.
__________________
Bob
Enjoying the GA coast all year long!
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www.freewheelspa.com