I'll take a wild stab at it.

All the way thru '65, the front drum was P/N 113 405 615A
and it used tiny ball bearings.

Beginning '66, the wheel bearings (and shoes) were changed
and the drum bores revised. The new P/N is 131 405 615A

If not careful, the numbers can easily be transposed and the
computer will ship the wrong part.

 

A '64 Beetle drum has an inner bearing bore of 62mm and an outer bore of 52mm.
A '66 has an inner of 50mm and an outer of 40mm.
Are you sure you have the year of your car right? Does it have king pins and link pins, or ball joints?

 

Thanks for all of your help guys. Turns out the car IS a 1964 but at some time has had a different beam put on it!