My m818 will do im guessing 70mph judging by how fast the traffic is passing me on the interstate. But I would be happy with doing 65 if it meant my truck would pull better. I don't care about going any faster the speed of trust travels is ok with me. I just want to get up to that speed faster. I have a m871 with 28,000 lb. On it, thats why my truck needs that power so I can put it at interstate speeds(60-70).
WILL pull a LOT better if you get rid of those big tires, 70 mph, is a little fast for those tires ( more like 55 rated), in fact a bit fast for a empty 818 on stock tires, let alone pulling a trailer with a load, sure glad your in TX. a long way from GA., a 818 is not a fast vehicle, not designed to be, it is not going to matter how COOL your army truck looks when grandmom and grandkids get hurt, will NOT HELP the MV hobby one bit.
If you want to run interstate, get a PETE, KW, ect, put the 818 sheet metal on it, most will not know the difference, still will not have the big tires, but things WILL be a lot safer. I can picture (hope you can also) the event (MESS) when one of those tires blow while the 818/871/14 tons of load is doing 70, OR a wheel cylinder goes as soccer pulls out in front of you, those first few seconds will mean life and DEATH (w/c goes means no air pack which means NO trailer brakes till the trailer brake control is used) . being that you were running way out of spec tires going way above the designed speed of the truck and tires, everything that happened will be YOUR fault. I would bet you would not handle it well if some GO FASTER ran over your family let alone in a old army truck designed to do 55, so why put EVERYBODY on the road at risk. I DO KNOW one thing that if my family or a close friend got run over by a go faster, my PTSD would NOT handle things well.