I'm not 100% sure which Curt gooseneck is on there and they use a template so I don't have the measurements handy. However, the # BWGNRK1020 does list the measurements so you can run a tape measure in your truck bed to see if it lines up.
Hook your tape measure over the rear edge of the bed at the tailgate end and measure 45-5/16" if you have the long bed or 37-1/8" for the short bed. If the measurement takes you to the center of your Curt gooseneck you have your answer. Depending on... view full answer...
It does appear you will want the Gen-Y Hitch 5th Wheel to Gooseneck Pin Box # GY58GR you found on your Dutchman Astoria 2993RLF. I can verify this is the correct pin box if you can give me all the information off the Lippert tag found on the mounting arm which the pin box bolts too. Otherwise you can verify with a few measurements. You said the bolt spacing is 8" but I think it is actually 7-7/8" from front to back on center. The holes will be spaced 2" vertically and the pin box will be... view full answer...
Since we are not 100% sure of the serial number on your 2015 Keystone Cougar 279RKSWE I recommend verifying the bolt measurements on the pin box. A 1621 pin box is going to have the 5/8" bolt holes spread 2" vertically and 7-7/8" horizontally on center. If you have something different please let me know otherwise the Gen-Y Hitch 5th Wheel to Gooseneck Pin Box # GY58GR is going to be the correct bolt pattern and weight range for your Cougar.
Do remember you will need Safety Chains # GY49GR... view full answer...