the 4 / 2 cyl switch is gotta be the jake/engine brake, 4 cyl will provide the maximum "engine" braking possible (on your truck).
the other switch is probably an AIR dump (probably for the suspension air bags, but could be something else too).
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Don R.
'04 Haulmark (M42386) 42', 2 slide, 10kw - Pictures
'04 F350 CrewCab Longbed 4x4, 50g aux tank & gear vendors dbl over
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