Little details like this are important to some, and I have recently done many hours of online research on the subject. I've studied sizes, shapes, colors, spare tire types and sizes, etc. Most 71 challys and cudas apparently used the hollow masts. All 70 and early 71s supposesedly used the t-type, maybe until they ran out?
There are several good threads on here about it, but basically the 70s and 71s used the seperate hook attachment which is shaped to the bumper (part #8931100). The elastomeric hooks were shaped slightly different and I think the last # of the part # was different. I think that part # is 8931101 iirc. These jacks and hooks are more rare and more $$. The slot type jacks used with 72-74 dont need a hook attachment and are not as rare.
Keep in mind that the factory may have often used whatever was available at that moment on the assembly line, so exceptions do exist. As usual, Dont believe everything you read or hear from ebay or craigslist sellers. I have noticed quite a few misleading ads, especially where 70-71 parts are concerned, since sellers can get a lot more money for them. Ive seen b-body parts, wrong year parts, or even gm or Ford parts represented as being for a 70-71 cuda.
In the end, since Ive spent an inordinate amount of time over the past couple months "upgrading" my bare trunk with jacks and a space saver spare, I have learned a lot and can now identify most of the correct stuff for each year. What a skill! Now I can be the official trunk inspecting a**hole that tells you at a cruise-in "hey, you realize thats the wrong valve stem cap for that spare, dont you?"
That said, because of the similarity of some of the parts, theres still a lot of confusion, and I still wouldnt bet my life the parts I've put together actually came from the factory in a 71 cuda or chally trunk. I also would certainly like to see some closeup pics of a known real jack body and the base, just to compare mine.
The only codes I know of are on the hook (with the pentastar), the base has a "U" stamped on it, and the body of the jack will have a date code stamped on the rivet head.
and btw, heres a "before" picture of my jack when I purchased it last month off ebay. Spent about 4-5 hours sanding, priming and repainting it the proper dove gray color.
