A check of some of our usual vendors shows they are listing/offering the correct style 1/2 ton master cylinder that has the same mounting design as John's picture.

Classic Parts 1936-46 1/2 ton MC (Currently listed as arriving soon)

Jim Carter 1936-46 pickup MC (Currently listed as out of stock)

Chev's of the 40's 1938-46 1/2 ton MC (Currently appears to be in stock???)

The various vendors like several I found on ebay, partsgeek and others advertising master cylinders for John's application often seem to not use the correct picture for the application, showing pictures of the larger truck master cylinders which mount with bolts through the body sideways. Even Google AI results shows the wrong pictured style. frown

Best to thoroughly review the part description and applications list before buying to be sure you don't end up with the wrong part. wink

~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)