Alan,
I have a L3600gst, it's a member of the Grand L series by Kubota. However if yours is a 3650 it's not the same series,
in reading this site for awhile, it seems that Kubota had a lot of tractor's in the 1980's which ended with the '50'.
I seem to remember a post on the old KTS site reguarding the L3650. Seems that it was a larger tractor (HP wise) than by 38hp L3600. I have formed the belief through my use & what I've read that the Kubota GST is bullet proof. 400 something hours is nothing, and I'll bet you bought a great tractor. Somewhere on this screen i'm almost sure there's a way to go to the old KTS(kubota tractor source) site and read the the arcives(is that how it's spelled ?)
Have Fun BOB