Lifter Questions

I ahve done the requisite thread search but still have a few questions.... I recently bought a Marshall Engine (4K miles ago) Started hearing what sounded like lifter problems...Called up Marshall they said "Gimme the serial number we'll ship you out some new lifters and a new head gasket" No problem right.... Well they got here, I pulled the head and removed the lifters. One of the lifters is about a quarter inch shorter than the rest and has a small ragged hole in the bottom of it. The botom of that lifter is chewed to heck. One "Mechanic" buddy of mine said put in the new lifters and move on. Another one freaked out at the idea of just replacing the lifters without more investigation. The first guy also said "Throw away those stock lifters and get you some roller lifters, they reduce friction and improve performance"
Do I call Marshall and demand new block, or throw in the new lifters and move on.
Thanks in advance for all the help, sorry post is so wordy.

gbXJ, is there any way you can inspect the cam lobe that mates with the bad lifter? If the cam lobe looks OK, then I would install the new lifter and drive it. If the lobe looks scored, then the cam should be replaced.

That lifter was probably defective when it was manufactured. (The lobe mating surface is supposed to be hardened). Generally a cam and lifters are installed as a unit, so they will wear in together. Since the cam only has 4K miles on it, a new lifter will probably be OK as long as the cam lobe looks OK.....

If the lifter is a quarter of an inch shorter, your cam is likely toast. Check the lenghts of the push rods, seems like somebody may have the lash wrong. That part of the motor wasn´t oiling right or maybe the lifter stuck in the journal, maybe the cam was defective or ground wrong, might have the wrong valve spring in there. I wouldn´t trust much of anything else in that part of the motor. Gotta wonder where the metal went and what damage it´s done. Only way to know for sure, is measurement and inspection. Have seen new cams shed material, when the cam wasn´t properly lubed at installation. Be surprised how many times, I´ve asked, if the owner, still had the original box for his failed cam, so I could check the numbers and found a package of cam lube, still in the original box. Without the lub. the cam will shed the hardened top material and get into the softer inside metal, works like an abrasive, looks ugly.
Roller rockers or whatever, are generally for high RPM motors, which the 4.0 isn´t.
I´ve occasionally gotten bad rebuilds, been lucky, usually only cost me the time and effort. The rebuilder made no big fuss and sent me a replacement motor, tranny or whatever.
If they get obnoxious, I ask/demand the moon and usually settle for an acceptable compromise.

Hey thanks for the help. I have since called Marshall engines and the folks in the warranty department have been very helpful so far. The tech there has lead me through troubleshooting and is adding up a good list of parts he's going to replace for me. Even paying the cost of shipping the old parts back to him. So far we are up to Cam, lifters, head gasket, head bolts.