Nice setup! It should be a solid platform for you. I've owned both a 93' f250 IDI and a 93' f350 IDI. I moved up to the 350 because of the crew cab and space for kids. Both trucks have carried my 88' four wheel camper grandby all over the place. From my experience with both trucks on many dirt roads the 350 rides considerably better with the D60 instead of the D50 on the 250. I never had any problems with the ttb but it was almost comical how harsh and ride was, pretty amazing the truck held together with the rattling and bashing. At least the 350 springs seem to have some give to them and aren't arched in the wrong direction. Both trucks were stock, but you seem to have a different situation with the swap. I'd recommend at least getting the stock 350 springs if they fit or even better doing the RSK which i hear is a big upgrade.
I can't comment on the turning radius since both my trucks were stock, that being said, multi point turns are a pretty standard routine with both trucks. Both my trucks were naturally aspirated so they were/are kind of dogs pulling grades at speed but they are very reliable and actually turn great mpg when cruising lower speeds on secondary roads. Make sure the SCA's in the coolant are up to date to ward off cavitation, glow plugs and relay are good, and the starter and injection pump is happy and you shouldn't have any problems. good luck