I did this conversion about 30 years ago! I had a '65 3/4-ton G.M.C.,with a 305E. I took the old canister to the F.L.A.P.S. with me,and they sold me an adapter. At that time,they had one in stock. If I'm not mistaken,I think it was the same one used on the early small-block Chev's. You may have to order one,these days. You may want to take your canister with you,just in case. hope this helps.