I did not want to clutter up his thread so started a new one for the subject. Here are pictures of the tanks and some measurements. The top screw holes on the 62 are 4 inches apart and the ones on the 63 are 4.25 inches apart. The lower tab for the third screw is in a complete different location. I can’t remember on a 63 but I don’t think you can put a 3rd screw in the bottom with a 62 tank. With the hole location different I do not think Oldsmobile would have used up old stock for the 63 model but I could be wrong.
I have thought that the tank you call a 1962 was molded with the side indention to accommodate the air conditioning coolant tube from the condenser? The 1963 A/C condenser tube must run through the core support in a different place or the 1963 washer tank would not fit. I have not looked close at a 1963 with two speed wiper/washer and A/C.