Only numbers on the carb body are 6R 3752 B.Does anybody know size and year?

Holley publishes this, http://www.holley.com/HiOctn/ProdLine/CarbList.pdf

but I couldn't find 3752 or 37-52 anywhere on the doc. What you want is the "List" number which is usually on the choke horn facing the front bowl. It will actually say "List XXXX"

No choke horn or any other numbers.