Three on the tree options

Unless you want to do some floor pan surgery, your options are limited to the A903 or an A904 automatic. The A230 has the same size case as the A833 four speed and requires the four speed floor tunnel. It will not fit without that because the transmission tunnel is too narrow. I've tried it first hand. It won't fit. lol If you don't mind the column shift and are going to stay a slant 6, the A903 is not a terrible choice. That's what I have in Vixen and it works fine. I am eventually going to swap to the T5 though and that will require pretty extensive floor surgery. They are small in the transmission tunnel area.
That’s what I needed to know on the A230, thank you sir.

Keeping the slant, and this is just a cruiser, no launching or burnouts. I want to keep column shift/bench seats so we can pile the kids in and go.

I have a ‘67 904 and the correct steering column already. But I don’t have the shift linkage or a driveshaft for the slip yoke(not a big deal) so I’m trying to decide what to do.

In my opinion the 3 speed on the column is just cool, and unique since most people pull them out for autos or floor shift you just don’t see them anymore.