There must be something different between the 48-50 and 51-52 gas caps because all the reproduction parts suppliers list them different and the 48-50 are less expensive. The fill necks appear to be different too.

I don't know for sure but thought the 48-50 cap was non-venting and the vent is in the fill neck.

 

DC lists the s/s B6TZ-9030-A fuel cap under the old 8A-9030 part number. Lists the 1932/50 fuel cap under B-9030 that was replaced eons ago by 11C-9030.

My ref sez: B6TZ-9030-A replaced 11C-9030 & 8A-9030. Later on the the 1950's, Ford added suffixes to these numbers.

8C-9034-A .. Fuel Filler Tube = 1948/52 all trucks. Which means the fuel cap fits 'em all and the parts catalog sez: 11C-9030-A .. Fuel Cap-ventilated.

The problem with repop sellers is, almost none have any Ford parts catalogs, have taken info gleened from...who knows where?

And while DC has part numbers listed in his catalogs, usually only lists long ago ancient part numbers, that Ford later replaced, sometime multiple times. The B-1012 lug nut is one example. After SEVEN updates, it's now E8AZ-1012-A!

Since most ppl cannot find these ancient numbers elsewhere, DC has a captive market.

Ford...is in-famous for replacing (opdating) 10's of 1000's of part numbers EVERY YEAR!