They make an adaptor for the crank you don’t need machine work to use. You can then use TF 904/998/727. You can use a TH400 once you get the adaptor too.
I would give the 904 a try behind the 290, the 998 was stock behind 304’s. Unless you are going with a bigger motor down the road then 727.
Sorry I don’t know the BW line up.
Dave ----

Have you seen the Ultrabell tranny adaptor for AMC's to use chevy transmissions? What is envolved in using these?
 
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