Bob, first off all 6.5 bed trucks are not equal. Chevy has the longest axle center, to back of cab distance, so best case. Next comes Ford, you guessed it Dodge/Ram is normally considered shortest.
Due to the variety, Chevy owners often get by without a slider. Ford owners, ME, can get by without a slider. I have used a standard hitch in a 6' 9" bed for 16 years no issue. A very alert/aware Ram driver, with a rounded corner FW, could get by with no slider in a 6.4 bed.
I would suggest getting a slider in a 6.4 bed Ram. B&W makes a good manual slider, and Pullrite makes an automatic.
For the Ram puck system the B&W3600 non-slider is a great hitch, and has adjustable arms, that can be set full rearward. However, this is a driver beware, that could cause damage, when not giving full attention!
Jerry