@ivegotlittlebutmuch
If you understand lifter preload, then, even though the 4.0l valve train is non adjustable, you can correct it.
ROCKERS
Unfortunately this would have been much simpler with those valve covers off. Inspect the rockers and pushrods for wear, they are probably pretty bad. If so, consider a new set of improved performance rockers from Delta Camshaft of Tacoma Washington. You can use stock/OEM but for the couple dollars more, these will out last OEM. Also he is the only bubba on the planet that has them, he made a big purchase many years ago, from the only source.
PUSHRODS
You may get 35k more out if fresh rods, then it will.need them again OR you can contact Smith Brother's for either a custom set or an adjustable set; the adjustable set will pay for itself after the first 35k miles, as all they will need is to be readjusted.
A erd option is a set of 2.9l rockers which are adjustable. They are however not direct fit, 6 if them will require a small margin of machining; also paying for itself after the next 35k miles


LIFTERS
I have yet to see a set go bad. Roller lifters are inherently going to last MUCH longer, less friction in their design, so less wear.
IMPROVED OILING
While it's apart, perform a complete tear down, clean inspect the rocker arms, often it not usually caked full of crud. After a complete cleaning, open all the oil orifices 1 machinist drill bit size. Then chamfer and deburr, this will improve the top end oiling and costs nearly nothing but your time ..)