Bolting the drum to a wheel is a great idea!
I think you can get a claw hammer under the seal and just pry it out.
The seals were being made oversize for a certain period and there's still some out there. The one's on my coupe came from a vendor and appeared to have been ground smaller on the circumference so perhaps this is a neccessary step that gets missed on some seals?
It would be a good idea to compare old and new with a dial caliper.
As for arcing your shoes to the drum, that doesn't usually get the job finished.
The shoes don't "float" up and down and self-centre on a Model A so you need to mount them to the backing plate and use one of several methods to make sure they will have full contact.
Most vendors sell a device which fits over the spindle and you rotate this gauge to mark the circle and grind accordingly.
The tracks can be tweaked a little to move the shoes as well.
Wasn't there a nifty plan in a Restorer issue a while back showing us how to make a simple centering gauge from PVC pipe? Hopfully someone remembers & climbs in here because I'm developing CRS
Another method is mounting the entire assembly in a lathe and taking a cut off the shoes till it's a perfectly centered circle.
Maybe you could find someone with a Barret Brake doctor...a grinder which rotates on the spindle hub grinding a perfect circle.
The goal is to have full brake contact with your drums from the startup, as opposed to miles of driving with only the top or bottom end of the shoe in contact as it slowly wears into a centered position.
joke : you know why sea lions go to tupperware parties?
Looking for a tight seal.
....sorry.