production racer

If by "side stand lug" you mean this thing then you should not expect to find it on a '71 frame.

https://andover-norton.co.uk/en/shop-details-2/15988/sidestand-lug-bracket-welded-assy-

Once upon a time I had a 1971 Fastback, and it had a particularly half-baked arrangement in which the side stand pivoted on a pin that projected from a frame tube — not in itself a problem, but the stand was supposed to be retained by a circlip on the end of the pivot pin. This worked until wear between the stand and its stop generated sufficient axial force along the pin to pop the circlip off.

The AN website seems curiously reluctant to admit to the existence of this variant, but apparently this was a 1971-only idea: see this post on the Access Norton site

https://www.accessnorton.com/NortonCommando/side-stand.21650/post-323188
 

Where is the VIN plate? On the headstock? Roadster position. The Proddie VIN plate was on top of the main frame top tube, at the back, where it meets the rear subframe. If the plate is not there, see if it has 4 holes for it there. It was moved there as the fairing for the racer had a bracket which clamped around the headstock, so a new position was needed for the plate.

There are various tell-tale differences, where the coils were mounted, for example. Under the tank? Roadster. At the front of the battery tray, Proddie. The oil tank is different; likewise, as you mentioned, the vented rear brake plate; etc.

It would be very unusual to convert a Proddie to full roadster guise; plenty were/are done the other way round, though!

Norman White has the numbers. They were on his office wall in his workshop at one time.

I am sure the club dating officer will have them, too.

This propstand??

https://andover-norton.co.uk/en/shop-drawing/473/prop-stand