I don't want to insult you Jim, so I'll assume you realise those things are from a different time when farmers not-infrequently were killed or horribly injured by machines such as that. Its use requires the utmost care. I doubt you could get any kind of accident insurance for its use, either.
I've seen them mounted on the tractor's 3 point linkage and driven by the right-angle pulley attachment often fitted to the PTO. That way you don't have to carry anything, and can do the job anywhere the tractor can go - which is saying a lot.
If that is a 26" diameter blade, I think 540 rpm is the speed that was traditionally used, for the same reason you have given.
You might find this discussion of interest:
http://www.practicalmachinist.com/vb/antique-machinery-history/rpm-cordwood-saw-270358/
