I think 254 could pretty easily get over the bump with 8 3.25 in wheels in a long drivetrain. They used low friction plastic along the bottom of the frame as well.
I'd look into pneumatic wheels just for the fact that hard wheels really do put a lot of shock into the frame when going over the bump. IMO 1114 or 610 were the best at getting over the bump that year.
1114 was 6wd long with (
http://www.andymark.com/Pneumatic-Wheel-s/309.htm) and some low friction plastic along the bottom and with a wedge in front.
610 you can easily see in the release video. (
https://www.youtube.com/watch?v=-7BG...6CD3AB2A804025) 8wd wide with a wedge from their pickup and pneumatic tires.