The difficulty of getting in the bed varies. There are workarounds but in general basement models are easier to get into bed but higher. Side entry is more convenient "if" you are pulling a trailer or have something else on the hitch. Otherwise, not so much.
The TC is hard to beat for being off the beaten path, but you should really go see some TCs in person to see if your are physically capable of using one or not.
Finally, a bigger TC also means a bigger truck. If you are buying a truck just for the TC, cost wise, you could be better off with a shorter Class C/B. The newer nicer TCs are expensive.
Oh, and mid 50s isn't old. :)