4.6 stroker for the win! LOL!
Actually, someone on the AMC forum has a no drill kit that has a crank insert and bellhousing spacer similar to the TH400 adapter I have below. Not EXACTLY the same, but similar. If I had a lathe and drill press/cutting table it could be made pretty easily.
You'd need a custom balanced flexplate (less than $200) and you'd need to decide which trans to run. I briefly thought about using a TH400 (Jeep with nailhead adapter) and Chev NP output shaft with the input gear for a Chev NP208 swapped into a Jeep NP208.
Way overkill for a 290, but it would be fun for a 401!
290 (and other '67-'71 AMC V8s) on left. '72 and newer on the right (same pattern as '72 up AMC inline 6 as well. Postal Jeep excluded)