8th digit is a 1 means it's 1st gen LB7. The biggest problem was injectors. At 155k miles it is probably on it's 2nd set. I don't have an LB7 but I think the injectors are good for about 100k miles, and I don't think they fixed the longevity problem (LB7 can provide their experience!).
As stated above, if the transfer case hasn't had a preventative fix made, the pump (in most cases) will wear a pinhole in the magnesium rear tail section, ATF will slowly leak out over months, and the transfer case will be destroyed. I suppose 1 out of 100 trucks will be lucky, the clips will stay in place, and they'll never have a problem. But most will fail some time after 100k miles (and a few sooner). Research "pump rub" for more info and prevention options.
Smoke? I don't think there should be hardly any smoke unless it's been tuned or the injectors are on their way out.
2004.5 Silverado 3500 SRW 4x4, D/A (LLY), Ext. Cab, Long Bed
engineer837 aux rad, TxC CAI, LBZ MP, Scangauge II, Nicktane aux filter head, KD lift pump, 2008 PS pump, 2011 hydroboost, Frederico Swaybars, Rancho 9000XL, Torklift StableLoads, BFG AT/KO2, Lance 835 Camper often in the bed.