I know this is dragging up an old thread, but I wish people would simply answer the question that asked, if they know the answer, and if they don't know, don't insert opinions unless prompted.
To refresh...the question that was posted was, in essence, what is the difference in these two ballast resistors? One has ana attached bracket, the other has no bracket and requires a longer bolt. I have the same question. I have a new to me 1972 Valiant that has the thick style resistor installed with what is clearly the wrong bolt...which isn't tight either. I also have a 1971 Scamp that has the bracket-style resistor with what looks to be a shorter, very original bolt.
Allow me to provide a quick demonstration regarding how to provide useful answers to forum questions instead of lecturing people on what you think is right or just talking to hear your head roar. Once again I had to answer my own question because of all the nonsense.
I dug through my on-the-road toolbox that I carry spares in because I recalled seeing a ballast in there. The one in there was another thick molded type, but this on had a part number...5206436, which is a very late Mopar number. With about 2 minutes of searching on the net and a trip outside to my '83 D150 to confirm, here is the actual answer to the question that was posted by the OP-
The thick molded type ballast is used on later trucks and vans, probably from about '81 on up. Those use a single ballast even though they have electronic ignition. There is one mounted right on the firewall of my truck, with the same part number.
The CARS use the single ballast with the metal bracket attached and the short bolt.
Question answered.