Well it is pretty much only the engine under the hood so you'd be good to go . I'd personally go with the newer engine.

 

There is nothing else under the hood that comes close to the expense of the engine. The tick can be caused by cracked oil pump gears, slipped cylinder sleeve (they let go after over heat episode), and more. With low miles, you can start a program of realistic oil and fluid change intervals, and monitor coolant temps with an after market mod like the Ultra Gauge ($70), which also reads and resets codes. Radiator will need attention most likely. With good oil, like Shell Rotella, and drain interbvals of 3,000 - 5,000 miles your engine can look like this at 200K.

 

most of the engine problem were with 03's very few 04's had the same engine problems as 03's.

30k on an engine meens very little IMHO, it all depend upon how the trucks were treated.

the engine in the second unit was not replaced because of a "gasket rod" there is no such thing. there is another reason it was replaced and you should find out.

I would look at the one with 77k, reasons being if it had a front cover problem like the 03's it would have shown up by now.

Also the drivetrain on the other unit with the replaced engine has 50k miles more on it.
So depend how many miles you drive a year; that is two to three years of extra wear that the second drivetrain has on it.

Once again it all comes down to how they were maintained, if you can drive a truck long enough for the engine to blow, how well did you treat the truck?
If you were in a battle with LR because your truck was rapping and they wouldnt fix it, how well did you treat the rest truck?

think about it? you spend $50k on a truck and when it starts rapping the dealer tells you to go pound sand, what are you going to do? thats right beat the **** out of the truck until it blow, then they have to replace it.