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It depends on the truck....
Ivan or Pros trucks worked great with 5.13s and 44s, and 600 + HP
Some times wheels speed is what's needed, and 6.17s isn't going to do it, or the truck is just driven on the street, and 6.17 is making the engine scream.
If you need something low, then there's always 4 lo.
no math.. u just upgrade to stronger parts and then you get a extra xfercase lever in the cab. they make kits for it. but just try it out with 5:13 it might work for you in 4 low.. the doubler is another 1000$ more or less.
A couple sites I just looked at offer gears as low as 5.38 for the sterling. I think D60s will go lower but the sterling is your hang up. Just keep in mind that your 351 wont like the stress of 44s unless you do major work to it. Your 97 computer wont like alot of the mods and you might have some trouble getting the hp you want from that engine. A efi stroked 460 might be somthing to consider or at minimum a stroked 351.
EDIT:
Basically mud is a MFer when you have heavy tires and thick mud.
i looked into 5.38's already. i plan on doing as many things as i can to my 351w. longtube headers, electric fan, new igniton/dist. stuff, cammin it and strokin it.
my ultimate goal would be to get a ford svo 460 in it.
ya allot of people i go wheeling with always cringe and say "man a diesel aint supposed to rev that high!!" hahah i look at them and laugh becuase it keeps on going! not bad for 250000 miles
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