A 2bbl? Only if you must!

Tom,
The only folks I know that would prefer a 2bbl to a 4bbl is in class racing where they have no choice. Otherwise, if you get a big 2bbl the big barrels will be soggy and unresponsive down low. So I'd stay with a 4bbl.

As for which one, other than the 1.12 4100 or the 1.08 4100 if you can find a good one:

I've had good luck with the Autolite 4300 on big blocks but not on the 289. On the 289, it is well behaved, starts good, runs ok, but will not clock as fast as a good 1.12 (or 1.08) 4100.

I've also had good luck with the Edelbrock/Carter/Weber "Performer" 600cfm carb. A bit big for your 289 though. Edel makes a 500cfm version that they say is just like the 600cfm except it has bigger (more responsive) primary boosters. Might be just what you need.

Summit Racing is remaking their clone of the Autolite 4100, not sure if they make a small one or not. I have not run these so can't comment directly.

As for Holley, the closest one you could get would be the Holley 450cfm. In fact, as List 4548 d0pf-u, this was a Ford part number service carb replacement for the 4100/4300 Autolite. It would run good on your 289 - a little less MPG than an Autolite but it will likely run faster, that is my usual experience. I think Holley still sells the 450cfm.