VCCA Home Forums TECHNICAL - 1945 AND NEWER 1971-1979 Letters On Frame

I have an Aussie built 1978 Chevy C20 , a number were imported by GM Holden and came as CKD packs (mechanical and body pack) and fully assembed and painted here as RHD . After dismanteling everything I am left with the bare frame
and hidden under the grime was this combination of letters and numbers stencilled in yellow on the r/h side . The first set is 5-10-78-2 ,I guess to be the date and 2 is the second shift, the second set looks to be FX-5717.462 the last 4 numbers are also stamped on the front of the right frame with S inside a circle after the 7. I know the S makes it an A O Smith frame and have seen pictures of numbers stencilled on frames but not letters , any info will be greatly appreciated as I can find little info on these, Cheers. (Not sure if pics will load).

Welcome to VCCA Chatter. I'll move this to a technical forum for you to get a wider audience.