1010 model differences?

I don't understand why there were different models of the 1010. The 1010 O is obvious with the full fenders with skirts to protect orchard trees but the others, the R, RUS, etc. are not so obvious. Just curious because I haven't found anything on the web yet which explains this.
Thanks.

I'll take a stab at the basics

R = row crop - Tricycle gear - roll-o-matic
RS = single row crop - non adjustable front front axle. Sat higher.
RU = Row crop utility - adjustable width front. I guess you could consider this the deluxe model of the 1010 line
RUS = Row crop utility special - adjustable width front. Basic model. Pan seat, 540 PTO only, No tach. There seems to be a lot of variations on this and some of the specials had some of these features.
C = Crawler - tracked model, 4 speed.

Thanks Skinny,
Why would a farmer or rancher choose a R instead of an RU for example. Were the different models intended for different applications? Would some models handle implements that others would not?
Inquiring minds........etc.etc.

If you haven't found Tractor Data then give them a look.

I could hack my way through an explanation but looked it up at Tractor Data Front ends and they can explain it better than I knew it.

There's really no performance difference in the different 1010s just how the tractor is set up.

Enjoy.

Well I never had and R model before so I don’t know the main difference for application wise,

but as for the RUS It seems as they were building them if they had an odd number of parts laying around they would just throw them on. Like skinny said for some reason the RUS had parts that were never meant for the special version.

As far as I can remember I have never seen two RUS that matched.