Check the inlet diameter on your radiator. It is probably 1 1/4". You'll need just the top section of the tstat housing to match. They are available with both 1 1/4" and 1 1/2" outlet sizes. They are identical other than the outlet size. Both sizes have the threaded hole for the fuel line clip. You'll probably need the 1 1/4" size to fit the inlet to your radiator. Your '57 235 would have come with the 1 1/2" size from the factory. They are usually available on ebay and are relatively inexpensive.
There are also versions of the top section that are for cars, not trucks. The angle and length of the outlet is a bit different and some don't have the threaded hole for the fuel line clip. You'll want to get the version that looks just like yours but has the correct size outlet.
The bottom sections are exactly the same for both tops, but are threaded for either a 3/8"NPT or a 1/2"NPT heater hose connector. This won't matter if you aren't running a heater because you will just plug the hole, but if you are, it might matter. If your bottom has a 1/2" hole (which they did in 1957), you can either install a reducer bushing or simply buy a new hose barb that is the correct size for your heater hose and has a 1/2"NPT male thread.
Matt
Great good to know. I will keep all that in mind. Thanks again
