I've had 2 Model A tanks chemically stripped.
They both went to Redi-strip in Victoria BC
...long since shut down when waste disposal costs overtook net income.
Both gas tanks went in rusty & grungy
...they came back with perfectly clean metal right down to the bottoms of the rust pits.
It looked as if you were to unroll aluminum foil and observe the dull backside of the foil...that's how clean they looked.
As far I could see inside with a flashlight, the tanks were spotless. I could not see behind the baffles.
Be aware that some lead solder around the...
filler neck, steering column support & choke rod support
...will be eroded away in the chemical dip process.
The original sweat-soldered seal should remain intact, but the lower supports especially need maximum strength and any missing solder should be re-applied using a torch and liquid flux to achieve a nice even puddle where the support-base meets tank.
Below...are pix of the filler neck -from inside- on a 31 tank that I had chemically stripped.
(The white coating is tank sealer which I applied later)
Visible through the sealer is a layer of solder, deftly paddled in a circle by some factory worker back in 1931.
This seems to indicate the neck was installed BEFORE the tank was welded together...