actually the problem there is GM used a variety of sizes and configurations, and the cars and trucks used similar stuff different years - I think the repro control valve was started by Danchuk for the 55-57 cars, which use the 'other' size [whichever], and I've found truck heaters with both 3/4 and 5/8 ... also, the lack of the capillary tube is "identical" to later GM replacement parts, which change happened before the end of the heater that had them from the factory
so if you're cheesed about the part not suiting your exact application, blame GM, but that doesn't define a poor quality repro part, just goes to show you have to pay attention to what's available vs what you "need"
Bill
