Different original rockers from factory

One style on each head. Is this common?

 

Im theorizing here, but MAYBE at some point early in the cars life, someone, maybe the dealer, replaced only one set of the rockers.
Could be the person who changed them because of ticking noise ( your chipped lifter foot) was told they're "service replacements"
by the dealer parts guy.
Im only theorizing here, as my '71 GS 350 had stamped steel rockers @ 88000 miles when I bought it back in 1985, maybe they were replaced at some point under warranty
Then a few years later when I rebuilt the engine I was sold the aluminum rockers
Then later on I replaced them with the steel rockers again.
Lots of stuff gets changed

 

My 71 had 45k miles on it when purchased in 76. Had aluminium rockers that were worn out. Dealer, (Fischer Buick) replaced them all with stamped steel under a silent recall warranty service bulletin. They actually just gave me the parts over the counter and I installed them.
Always thought about bronze bushing the aluminums, as they are 1.55 ratio opposed to 1.5, but that might take some strength out of them....

 

So my car originally came with the aluminum rockers? The other head has cast rockers? Which ones should I replace? Thinking I shouldn't put it back together that way.

 

Whichever style are in the best shape, wear wise, get another set to match. Not going to make that much difference in a stock motor.

 

Heads being built up from parts available. At some point, new parts used. This engine has a head from the "old" run, and the other head is the "new" run.

Maybe...

Wasn't there a point where some heads had a mix of both rockers?

Production is a funny thing. Often different stock is introduced for several reasons.

One may think, it is a "perfect" linear process with exact and specific parts being used.

But look at things like fasteners, and sometimes internal trim components being used even from other divisions.

Getting production done, sometime over-rode the "printed" instructions and pushing finished units out the door, was the greater factor than "perfection".

 

I think I read somewhere that the stamped steel rocker were a different ratio than the aluminum rockers.

1.55 or 1.5 vs 1.6...

 

I've heard that too, BUT, Im sure Buick didnt keep the ratios THAT accurate.
IMHO, I believe it was intended to be 1.5 BUT it could also be 1.51, 1.52. 1.53 MAYBE 1.54 or 1.55
If you want accuracy, get TA's roller rockers

 

I would re use them miss matched, not a big deal and I’m not surprised. If I had to guess I would say an alum rocker failed someone put a steel rocker on. The alum rockers tend to be less sloppy but more prone to breaking and the steel ones are more sloppy but almost always reliable.

Heck I’ve torn down a bunch of 350s and the strangest thing I’ve seen was 7 73-80 style connecting rods and 1 68-72 rods???

 

So if both sets are in good shape I'll just put it back the way it was. Worked pretty well for 140k and 50 years.