So, random_james, did you ever get the numbers for all the beds? I see Kevin M. gave us the actual dimensions to the king bed in back (thanks Kevin). Another user just said to use regular sheets. But does anyone have the actual dimensions to all the other beds in a 364TS? Or does anyone know where to look for them. I can't seem to find them either and my DW is asking for the EXACT dimensions for other reasons (I think she's going to do some sewing).
I realized that, while the bunk mattresses are gone, I still have the space where they used to be! it measures 33" x 72" and that should be pretty close to the size of the mattresses too. Hope that helps.
On the bunks, we use regular twin sheets and have elastic clip on straps to pull them tight under the mattress. We also have fairly thick memory foam toppers on them, a mattress cover, then the sheet.