I just did this last week, and have had no problems "going tubeless". When we removed the old tires and tubes, both the Goodyear guy and I looked closely at the rivets holding the wheel center to the rim. They were tight and appeared to be sealed with a heavy layer of a clearcoat-like material.
I imagine if you had some rusty rims that had been laying around without tires protecting them, it would be worthwhile cleaning and sealing the rivet heads just to be on the safe side. (I've seen people use a few wraps of duct tape for a seal, but I ain't going there).
The only other thing to be aware of here is that the stem hole is for inner tube stems, which means the hole is bigger than normally used with tubeless stems. Trailer type rims use a bigger tubeless stem, so those will be needed.
