The point Xram53 made concerning the replacement block and the 51 serial number being stamped on the block possiblly by the mechanic is good one...The "JAC 760064" is actual stamped on the block. The numbers and letters are not even and appear to have been done by hand. The other numbers on the block---J163 and 3835849---are raised and appear to be cast into the block when it was made. In addition, the place on the block where the "JAC 760064" is appears to have been machined flat and does not have the factory blue paint applied. Xram53's comments concering possible replacement reminded of the time my uncle, the original owner who is unable to communicate with me now told me once several years ago that he "ran the ole truck dry of oil back in the sixties."

On more question...How do I clean the interior of the fuel tank without removing it?

Thanks for the info..

Eightfan