To go 70, you'd want a different motor and a different transmission. The company that made higher gear ratios for the axles, don't make them anymore so finding one is extremely difficult and if you did, it's gonna be very expensive.
I know the custom built trucks, they make them so to cruise going 65-70 but also, they have power steering and everything is completely gone through.
For a faster cruising MV, better off doing a humvee or something similar. For a deuce or 5 ton, it's safer to keep the speed down, mostly due to the suspension and brakes. I know when I got my second deuce, driving from TN to MI, at times going over bridges, construction zones, RR tracks, where there's decent size bumps, the truck jerked hard to the side in which tire hit first or the tire that hit the bump. Kinda scary imo. Like driving a normal pick up with no stabilizer bar and if you've ever driven one with a broken link or two, you know what I mean, and this is in a deuce going 65. I ended up slowing down to 55 and kept it there. Felt a lot more comfortable and the jerking wasn't as bad.
At least if I wanted, I could go 65 on a smooth road no problem, but the rpms are high and I'd like my motor and stuff to last so 60 at 2350-2400 rpms is the fastest I'd go and that's only for a short period.
If you want a deuce that cruises like a normal semi, be prepared to dump a ton of money and time to get it there or have a shop like C&C or Boyce give you a quote on something that's capable of doing that. This is just my opinion