Truck Camper with out wings.

Northstar makes a camper specifically for a flatbed truck:

Northstar American Hero Flatbed Camper

1. I'm running a 60" cab to axle flatbed. Unless you plan to add storage between the camper and truck, you will have a lot of unused space that is hard to access with a utility bed. Ford allows space for dual tanks in it's shorter chassis cab, but Ram requires the longer wheelbase to fit dual tanks.

2. Most of the flatbeds and utility beds are 8' wide. Unless you get to the largest truck campers (which are 8.5' wide), most campers are also 8' wide. I would guess that you could have the wings trimmed flush with the rear camper storage boxes.

3. Many utility beds are too narrow internally for the "mini wings" that allow the floor to be wider over the wheel wells (like my current Arctic Fox). The largest truck campers start the floor above the bed rails and typically do not have the mini wings. Utility beds come in different heights - Unless you choose the low profile model, the widest part of the camper will rest on the sides instead of the floor. You will need decide if you go with a low profile bed or use a platform to raise the camper higher up in the bed.

4. Some of the campers put access ports on the underside or forward wall. Take a close look at these when designing a bed so you do not block access to fresh water or tank rinse ports.

5. If you plan to tow heavy behind your truck/camper combination, figure out your receiver and extension before selecting a bed. I chose to stay with TorkLift and had to find a bed with a low rear skirt to clear the large SuperHitch Magnum.

You lost me with the "3500 gvwr" statement.