Kinda guessing that's a 1967 Cadillac 429-to-BOP adapter. One year only, and only for ElDorado. If I'm right, I want it. I have a series of photos showing a '67 Caddy and TH425 transmission, but not on this computer. I'm gonna have to dig around to see if I can find them again.
Thanks for that. I did locate my photos, one is very similar to what you posted, the other shows the matching crank-to-flexplate spacer that is also required. Clearly the OP's adapter is something else. I don't know what.
The adapter looks like like the one used for the Jeeps which used the Nailhead case TH400, up to around 1973. Likely for the Buick V6 or 350 engine? Here's one on eBay, and a post from the cj5 board with more info: http://www.earlycj5.com/xf_cj5/index.php?threads/th400-to-engine-adapter.31293/page-2 >>> Sorry, no mystery. That's a NAILHEAD pattern. Search the net and you should be able to find a pic of a NAILHEAD V8 with the back end showing. There were 4 different adapter rings. 1) AMC 327 2) pre-71 232 (not the later AMC 232 - similar but not identical engine) 3) BOP pattern, 225 and 350 4) AMC 232, 258, 304, 360, 401 There was a changeover to an AMC-pattern case ca 1973. <<<< https://www.ebay.com/itm/JEEP-TH400...202249104234?_trksid=p2385738.m4383.l4275.c10
I knew the one side of the adapter was for a BOP, I'm not familiar with what the other bolt pattern is.
The rounded top with starter on the drivers side is a Nailhead bolt pattern. Jeep used the Nailhead TH400 transmission in some of their applications, requiring the use of the adapter to mate with the AMC or Buick engines.
They don't but the rocker arms themselves may interchange I'm not sure, but they certainly are similar in appearance. But the shorter assembly is for a 350 tho
