Thanks a lot for the good advises, MoparforLife.

Most what I'm concerned about is, as you noted, what happens if a bearing fails and loses a pieces straight into the engine. That's what I'm most afraid of. Did it happen? Is there something known?

The rattling noise I guess is coming from worn out rockers or shaft. Think I have to check this first. But they are now 30 years old. And why should I purchase a new OEM set if a Roller Rocker Set does cost similar?
Hm, I will ask a buddy if he does have a set for lend.
Cam is new, slightly hotter than stock 340, custom grinded to my car specs. Lifter & pushrods are new.

I not defenitly in need of roller rocker - I'm looking for "better than stock" because I have to change so I thought why not roller rocker.

Thanks again so far.