On another forum I'm on a guy claimed that he made a spray bar for cam/lifter oiling and that reduces chances of a cam failure to almost zero. Is this credible? A lifter with an oil hole at the bottom should achieve the same effect shouldn't it?
Has anyone ever made one for a BB Mopar engine?

Simply not needed.

maybe they talking about an alum block that originally had "dry " lifters. My block was/is like that. Each lifter boss is drilled/tapped and a supply is plumbed. Mine has one nitrous jet in the feed to limit the oil. it is plumbed similar to a nitrous direct port system. this also allows pushrod oiling. Not sure if this is what your looking for

Not needed in a stock type block that is, maybe it will be needed in a after market race block though

IDK anything about what's needed here, I defer to those who do.
If you decide you need this: IIRC when using a single restrictor (which is safer because its larger ID is less likely to clog from debris) the individual tappets should all be fed in parallel (branches from a central block) or there will be a pressure drop for the ones at the end of the chain*.
Math (my OCD): 16 × 1/32" = 1/8"
Small radius on both ends of the 1/8" hole increases pressure and delivery rate.

* applies to boosted manifolds

Gobs of oil flowing down from the heads, gobs of oil flowing out around the lifters, oil spray up from the crank. Seriously, was this guy talking about Mopar engines ?!?!?!

While spray bar oiling for the HEADS can be debated the cam and lifters get Plenty on almost every block that I know of for BB or Hemi mopars. To the point where we actively try to get some of it out by using external drains on race motors.
heck we used to cut the oil supply off at the back of the engine to the drivers side lifter bank and they ran just fine. The right oil, spring pressures and correct assembly will keep the vast majority of flat tappet cams chugging along just fine/
Todd