2manyprojects

hello all.

New to the forum but i have a serious issue new to me. I'm working on a 95 [i believe its a 95] cheyenne p/u. 4wd reg cab long bed if that matters but anyway here is my problem. The engine knocks erratically at idle and at higher RPM's. Almost sounds like a upper engine knock but hard to locate exactly. I pulled the valve covers to check for a bent or broke push rod and they all were tight and seemingly not broken, all lifters moved as they should and when pressed on while running continued to move. Then I noticed that only the center 2 were squirting oil on the passenger bank while on the driver bank i had only 1 that even seemed to attempt to pump oil out and the rest don't push squat and by squat I mean doesn't appear to even try to squirt. I'm trying to decide if it is a simple in truck repair or if i should go ahead and began pulling the engine to put in another 4.3 he has. Ideally i'd like to do in truck fix because he bought an 89 p/u for the motor and if i can avoid the dreaded RnR of the engine he'd have a second truck to do what ever with and I wouldn't have to pull motors and such. Any help will be greatly appreciated. Oh and its a TBI non vortec engine.

Thank you in advance.
2manyprojects

[my wife gave me that name due to the 2 6.2 diesels in the yard i'm working on.]