I bought a 425 last year on Auction Time last year in NE. Pulled it to IA to pick up a JD 925 head. Put some magnetic lights on, tied it down, and pulled it home 400 miles on the interstate going 60-65 mph. No problems. I will just be making short hauls with it now, so it fit the bill here.  Two neighbors have 435's they haul JD 635's on and seem to be pleased. I think you have pointed out the obvious in the 400 and 800 series, any other differences I am not aware of; but never really looked at the 800 series. The 400 series does not have tie down straps, I am not sure about the 800 series.