Emma has about 325k miles, I have been running her as a DD since I bought her used at 180k. My commute is 100 miles on the nose each day. 3 days after I bought her, she was tuned with about a +140 tune, and I have never looked back and just gone up in the tuning from there....
Over the years I have done:
Kennedy twin pumps, with Cat water seperator and fuel filter
New S366, T4 at ~220 when I blew a hot side boot and took out the oil seals on the IHI,
Built trans when I finally killed the stocker at ~250k and a lot of laying the whip with the tune,
Head gaskets and studs at ~260k after running with a blow head gasket for waaay too long,
SAC 65% overs at ~280k, fuel in the oil and decided to go big
a 10mm Fleece CP3 to keep up with the sticks at about 290k
Mark B at Danville did a great job of tuning the truck after the new CP3.
Rebuit the stock filter head twice, now have a new one (tired of the leaking). I keep the stock filter head for the primer pump to charge the Kennedy centrifugal pumps as they will not self prime.
I have also rebuilt the t-case at ~200k because of vibration (bearing), had the front diff rebuilt because of a leaking case at ~300k (more tired of the oil on the floor than anything else), plus just regular maintenance.
This has been a great truck, and I would not be worried about driving her to Florida if I wanted to go that far. These things just keep running if you take care of them.
If you need the sticks or pump, I would use LDS. Those guys have been fantastic, have great parts and customer service. If you make a call, they will give you everything you need at really reasonable prices.