I said M35A3 I did not say M35.An M-35 is NOT a great and easy route. With 600 gallons of water you will be OVERWEIGHT for off road. And Pods are not baffled which will increase the danger. Not to mention no ROPS. Unless they are purpose rebuilt by a commercial brush truck company, FD's should stay away from M35's. There are plenty of NIOSH LODD reports to back that up.
1.) A full 600gal pod is 5400lb. Add a couple FF equipment etc at NFPA1901 and over the offroad 5000lb payload rating.
I have 10 baffled pods I picked up from DRMO sitting within 100ft me. You can come see them if you like or can get you a interior photo. NO not ALL pods are baffled and without looking inside you can't tell. Perhaps with the mfg date. I'm told baffles were added to later pods but have never seen what date that would be.
I'll stand behind one pod in a M35A3 is a great and easy solution for a rural FD wildland rig. Go to Roscommon if you want more great info of converting DOD vehicles (appropriately for FD use.
2.) ROPS? you have a ROPS on your F550? Given what is available DOD surplus the M35A3 is the best medium size option available. I have a 4x4 IH that got from AF surplus but not may of those available. For manpower limitations of modern/current FD the A3 is the only version of the M35 I'd recommend.
Ever seen a M35 with 1500gal? That's something to be concerned about. 600gal NO
Last week I was in a fire station and there was an M54 with a 3500gal tank. Now THATS SCARRY.