If you go for a rebuilt ready to go carb from the big box stores? Stay away from anything TOMCO carb.
Got a good bus graveyard in Washington NC if you can pass the grumpy old mans test to walk around his backyard.
Wanting to go back there soon but not within this month but If still needed I will let you now what I find when I go.
I don't know that Holley was the original carb on that motor but was a good upgrade.
Your profile says your bus is an 1898 model? That would trump anyone here