1971 Norton S/S front wheel

I have just about everything ready but I need to know what size the wheel is to be.First I have a complete S/S that I had at the International Norton raly in Lumby B.C. and It took a award Its Orange and has the original front wheel 21" there were some that said that it should be 19".Now last summer I found another 1971 S/S and It has the 21" front rim.
Did the ones that came to Canada have the bigger wheels?
I wish that I was better at photos and how to attach them .Is there a simple way.

I thought it was 20 inch . :lol:

looks like a 19 in. here , http://classicbike.biz/Norton/Brochures ... mmando.pdf, in this cattledog .

Thinking 20 in the road test of a early one .