Hi Alex.
Welcome to this great forum.
I was in a similar situation, I had left my bike standing for 29 years, but decided on full rebuild. The engine was in good shape but as I had stripped it to investigate condition, went for rebuild with new bearings and seals plus new rings. The shock for me was the sludge trap, the crap inside was almost solid, with no thro route, similar tale in the bottom of the oil tank, thick crap.
My recommendation would be to remove the oil tank filter and feel around the base of the tank, before you decide to risk starting her.
With regard to the mag, mine just needed a good clean, same for the carb, even the dynamo worked, with no other than a clean.
My tank was left empty, and did not suffer from any corrosion, never been lined.
Investigate best engine oil choice, but I think secret is to change on a very regular basis, and don,t forget leaded additive for the fuel.
Best of luck