2bbl to 4bbl conversion?

I don't think Mopar ever made a 2bbl so big you couldn't run two of them at WOT on any 318 to 360
Trying to get the car moving is another story,lol. Ima thinking lotsa rear gear, a bit of a loose TC, and lazy low-rpm timing
I would not "seal" one carb. The transfers have to be operational or no matter what, you will have a tip-in sag, until the dried up transfers get moving.

I've never run two of those So I can't help except to suggest lazy idle timing. The lazy timing will require a larger throttle opening. With a small cam, you may have to restrict the PCV to a smaller idle feed. This too will require more throttle opening to compensate.
If it was mine I would set all the transfer slots to square to a little wider than tall, and reduce the fuel level at least a sixteenth. Then I would set the idle-speed with timing and restricted idle-bypass air. but I wouldn't touch the Curb-idle screws again after the sync was set.
I would start the timing curve about 150 rpm higher than the idle speed. The rest of the timing curve is compression and rear-gear related. I would not be in a hurry to get to max timing but I would try a two-stage curve with about 28* at 2800, then slowing down.