5th wheel hitch suggestion

You are on track with your thinking. You didn't use the slider with the Ram, and now the Ford will work even better. It isn't the bed length though, as much as it is the distance from axle center, to the back of cab. The Ford is giving you several more inches of clearance in this case. No, you don't need a slider!

The 3300 is by far the best choice for your new Ford! You just upgraded to the best truck, may as well put best hitch in it!! You will love them both!

Congrats on the new purchases,

Jerry