This has worked for me in the past:
Take off one of the float bowls and set the float height. Then remove the drain screw from the bottom of the bowl and stick/screw a clear plastic tube (small dia from hardware store 2"-3" long or so) in the drain hole and reinstall the float bowl.
Route the tube straight up and open the petcock. You'll see fuel fill the tube as high as it is in the float bowl.
Make a mark at that level on the tube and then just swap the bowl with the others to check their levels.
(or, conversely, swap the tube to the other bowls)
In general though, new needles and jets shouldn't appreciably change your float levels.
The little brass tabs are fairly delicate, maybe you bumped them during reassembly
(been dere, done dat'
)
Take your time, you can do it with the carbs installed.