mine has the 5.9 (old "360 cu. in") engine, currently has 258K miles, rust free which is rare around here. Bought 6-7 years ago with 214K on it, like a month after it arrived from Louisiana. not interested in anything with a 4.7L, no experience with those at all....
I bought it, knowing at the time that I'd probably be putting an engine into it, because it was so clean, but it had highest miles of any vehicle I have ever had did, at start of me buying it/owning it.
Had been a very good dependable vehicle for us, until a computer issue that gave me a chronic #6 misfire on the orig engine. I actually got more out of it before the "inevitable" happened than I thought I might.
Issues with the misfire started around 252K miles.
Did a compression test on that bank (numbered just like a Chevy, odds on driver side, evens on pass side) 150 straight across.
Complete tuneup with the "better grade" of cap rotor wires plugs (it was due anyway, almost 40K since I did the initial one when I bought it) No change. At first it would show check engine lite but couldn't tell it had an issue by the way it ran. That changed.
swapped injectors between cylinders. Still misfire on #6. Took injectors in to a Bosch fuel injection place. flushed, tested, rebuilt. All good, "just needed a good cleaning"
sent computer into computer rebuild place I found online, they went thru it and found issue. Got back, issue gone. but came back.
in the meantime oil pressure started going goofy, but typical of high mileage. Time for the engine swap.
I went to CL and found another, took that one apart and sent to machine shop for anything it needed. Bored, hot tanked, crank polished std (this engine didn't need crank ground) I have cam bearing tool, put those in myself.
Also rebuilt trans "just because" I didn't know its history and "because I can". also new fuel pump along with new engine, again "just because".
Assembled short block, all clearances were spot on, put original cam back in but new lifters and all new pistons, rings, T chain, oil pump,gaskets, etc.
Bought BRAND SPANKING NEW "EngineQuest" fully assembled heads. 3rd set of these heads that I have used on various projects, 1st 2 sets were great. Original Mopar Magnum heads have tendency to crack, so I decided to splurge for the new heads.
got it assembled and installed, started right up without even a lifter tick, as I ran the oil pump with a 3/8" drill while on the stand to verify pressure and prelube everything. Ran @2000 RPM that 1st nite for about 45 min/maybe an hour. 2nd nite. stared and ran, monitored scanner and gauges, warmed up, so far so good.... 3rd nite with new engine.... test drive time. I never was able to achieve 50 MPH.. Huh???? Check engine light and codes galore, stalled 3 miles from home and couldn't get it going, exhaust was glowing like red neon, melted down brand new cat....
get it home, got it going next day, but not well.... found out injector on time at idle was 5-6x as long as normal for idling engine. Different wiring harness... no help. different computer.... no help. added redundant grounds.... no help. sent both original and replacement computer back in, they found issue with original one, said they had canned orig tech that worked on that one the 1st time, theyd had issues with this person. They both redid that one and programmed 2nd computer for my VIN at no charge. Cant complain about that.
Meanwhile, I decided that 2-1/2-3 hours was enough run time on break in oil. When I went to drop that oil, I found a slurry of bearing material. At that point I threw up my arms and parked it. Never had that happen before. figure excess fuel "washed out" cylinders and new rings, like when a float would stick on a carbd engine in older days. this was Nov '16.
fast forward to last month. found another 360 on CL, lower miles than the 1st, 125K less than whats on the body. Figured to just drop it in, but "well Id better replace gaskets and freeze plugs while access is better than in chassis". Head off issues, sort of thinking. OK, I'm pulling the heads for new gaskets (I have a stack of em ere, just because I found a "deal" on them) OK the "might as wells" kick in. I want my new heads on this shortblock, have this engine apart anyways..... and when I went to pull new heads off of the 1st overhauled engine that's when I discovered the problem.... never dealt with that before.... so I sent those brand new heads thru the machine shop and they found a lot wrong with them....
so I started googling and it seems that Enginequest went thru a bad spell around the same time that I bought my set of heads.... same problem as I experienced.... would have been warranty if I had gotten right to it (1 year warranty, its been 3) but I don't think they would have done anything for the collateral damage to the short block, so I'd be out that money anyways..... too late to see what they would have done now.....
in the meantime I pulled the pass side head off of the original -original engine, crosshatch still visible in cylinders even after all those miles, cant see anything wrong with original head.... my son wants that engine to rebuild for one of his "projects"