I made my picks, but I'm in agreement with Andy on this point...... Test the ones you think will be/want to be the best first.

Edit- after hearing Doms comments about the 6a being a little fat..... I guess I'd start out with the known quantity tune of the #1 carb.
No point in risking washing the rings down right off the bat.

I'd do the initial run it with the #1 carb, get it all warmed up, lash the valves, make a couple pulls ...... And hopefully that carb has a decent enough fuel curve to establish a baseline without having to do a bunch of tuning on it.

The next carb I'd try would be the 6a.