The one like it up here was listed for $4K recently and I assume it needed a bit of work. Like the old Dynahoes, these machines were built to work hard, and likely did not evolve from a farm tractor. I'd put the value of that at about $6000-$6,500 if it worked good and the rubber was good. If sold in the spring, no one would be too concerned about the lack of cab and it's probably more enjoyable to run anyway, without cab vibration.
There was a picture of a restored one here, but not sure which thread. It showed what was likely the correct colour for the wheels, but I can't remember what it was. In the UK these are highly thought of and I believe there's lots of JCB's there. The name Digger Doctor comes up once in a while, for parts and support. Phil