A: 105 bed is a perfect fit for the back of a 818.
B: The 5th wheel itself comes off VERY easy!
C: a 5th wheel pin between the frame rails of the 105 trailer make for a strong setup...
D: a second set of ramp mounted upside down to the 105 frame will brace the rear very well.
E: racheting binders are easy to setup for the front.
Basically, if you have big super singles, you NEED the extra height from a bed on top the 5th wheel. If you have stock-ish tires, then taking the 5th wheel off first makes more sense.
MY plan.
I have a spare 105 bed. I will take out the wheel wells and move that metal to the outside to make a STRAIGHT bed out of it.
I was planning on using the 105 frame as the subframe from the bed, and have the bed permanently attached to the frame like the stock bed frame was. Then weld on attachment points to the frame that would go down to the angle mounts for the 5th wheel.
What I haven't finished figuring out, what height I would need to keep those tires from hitting the bed under extreme articulation. I did a little testing, and see that the tires have at LEAST 12" of upward travel. I imagine they will move a bit more, but I didn't have a good cliff to run the truck up
If I need more height, I will either use the 5th wheel setup, or add a frame spacer under the 105 frame. Depending on how much height I need.
I would prefer to do the 5th wheel setup, but I need to find a 5th wheel pin like mentioned above, that is CLOSE to me. Shipping kills any savings on that deal...
Btw, the 105 bed leaves room to leave the stock tool box, spare tire and wiffle tree setup all in tact. Even have enough room for putting fuel in the driver side tank!