I would also point out that, prior to 1972, AMC/Jeep did not include the year of manufacture in the VIN numbers. That 1971-registered Wagoneer could be a '70 that sat on the lot and was newly registered in 1971. We see this a lot with CJs - the year on the registration does not always conform to serial number registry.
Unlike 1972 and later, the sequential serial number part of the Jeep VIN was not reset with each new model year. You can more-or-less determine the date of manufacture by comparing the serial number to the registry. Some of this registry data (for CJs) came from old factory records that were saved by enthusiast, and some comes from reported serial numbers of owners.
If it's actually 1970 production, it could be a Rambler 232. I recall you can identify these by the starter located on the driver's side of the bell housing. '72-on are all on the passenger side. I think I encountered a claim that the '71 transition engine had the starter on the driver's side, but I'm not certain. There may be a picture in the parts book. The ring adapter has to change in '71 because the bell pattern went to the "unified" V8 pattern. (Apparently not - see below.) If there is a separate adapter for the '71, that would indicate the starter side changes in '72, not '71.
ringadapter.png
You can look at the book and find this illustration in group 1, though these parts are listed in group 6.
Only some applications used the crank adapter, 6.521-1. All used the ring adapter, 6.525-1.
6521dash1.png
6525dash1.png
This is surprising - I would have expected all 258s to use the same ring adapter, since that only depends on the block pattern, not the crank pattern. You can see that the crankshaft spacer only applies to the '72 and up, and is the same for all AMC engines, sixes and V8s. This implies that the bell pattern for the sixes did not change until 1972, and there were 1971 258s that had both the earlier "Rambler six" pattern and no crankshaft adapter. Huh.
(This also implies that the 232/TH400 combo was available in the bullnose Commando. Also huh. I have never seen one. The "unified" 232 was not offered in the Wagoneer or J-trucks; that's an error in the listings.)
If my time/effort were limited, I would trust the parts book and reject any six engine with the starter on the driver's side. Either it's a Rambler 232 ('70ish) or a transition 258 ('71ish). Both will have the wrong bell pattern for your Jeep.
Sorry for my geeking out on this, but that's how you learn. Pick a problem and try to solve it.
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