I like Rochford for foam purchase, very good outfit.

Assuming you are talking about front couch/bunks. Dimensions probably won’t help as there are quite a few curves. I would make cardboard templates from the bottom bench for sofa cushion. The back cushion it would be helpful to template off a trailer that has bunk in place, or if you order covers from Scamp use them to make templates.

Biggest tip: Use an electric knife to cut foam. Cuts like butter and you can get one for about $12.