Petter, My is also the same except for being a 5 speed. I am at 86,000 miles and have had mine since 72. Hopefully I can help you.
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Dee'sel
97 2500 Club 4X4 3. 54 LSD 5 speed, K&N Air filter RE0880 & Psychotty,
TST #11 all the way forward, #12 for winter, AFC spring kit, Geno's Exhaust Blanket
TST EGT gauge & TST 0-60 boost gauge in A Pillar, Hypo clutch ass.
Cat-be-gone, 4" Dynomax Bullet muffler, Crome 4" turn down,
AmsOil 80W-90 in Trans GL-4, Amsoil 15W-40 Oil W/ Bypass system
Lund WInter front, Leer Cab Level Shell,
235/85R16 Goodyears *NRA/USPSA member and proud of it*