Rookhawk, I think your numbers are fairly close. As far as I know, of the 974 Gibbs Farquharsons, most were Match Rifles and what are known as Military Match Rifles or Military Breechloaders as they are also known. Probably 375-450 of the total are of these two categories.
The Sporting Rifles are more rare making up about 350 and the Rook Rifles around 200.
These estimates are explained in Winfer's excellent book on Gibbs single shots.
As far as I know, there weren't any originally chambered in 500NE. A few were in 500BPE though.
A couple 450/400NE rifles were made toward the end of the production run I believe.
The other nitro chamberings that I am aware of are 303 of course, 256 Dutch Mannlicher (6.5X53R), 280 Flanged Magnum and 360 No.2.
Unfortunately, all of the ledgers were lost in the German bombing of Bristol except the ledger of the last ten or so rifles.
Of note, is that Gibbs made Farquharson rifles in at least three action sizes. Rook rifle sized actions, medium actions and larger actions. I've never had a Rook action but have a 303 on the medium action and a 461 No.2 on the larger action. There was a gradual evolution in the action as time went on - consider the 974 were built over a period of 35yrs or so - 1875+/- to the last in 1910. Almost no two are exactly identical.
That is the shortcoming of the Ruger No.1 in my opinion - one action fits all from 218 Bee to 450NE!