From what I have read, the 245/70R19.5 tire will fit in the stock location on the Ram and Ford. The GM's seem to be a little tight and may need to be deflated to squeeze in. I know my F250 could carry that size 19.5 or a 275/70R18 tire even with the larger SuperHitch.
The next question is how you will access the spare. I was able to use the jack extension to reach the crank mechanism to raise or lower the tire. It was easier to disconnect the lift chain and pull the truck forward than drag the tire out, but all could be done with the camper secured (I have a big bottle jack for lifting duty). Those with more than 2' of rear TC overhang need to build a longer extension or relocate the crank to the rear wheel well opening.