Let'* say you put a harmonic balancer from a '98 L67 on a '98 L36...would it work?

It'* definitely been done before, on other years at least.
(I've seen a bunch of full L67 top swaps)

I guess what I'm asking is, would it work without the rest of the top swap being on there...

That is, suppose you did a full top swap, then--for some odd reason--had to swap your L36 UIM / LIM back in temporarily (and of course remove the */c belt)...would it run right?

(Maybe it'* time to move this to Performance forum?)

Yes it should as it'* balanced and only has the second level of ribbing for the second belt. That shouldn't affect performance.

As long as the timing rings are the same, it will work.
The inner belt path is the same as the L36

No. (Ok, I'll re-phrase that as "maybe")

It will fit, but it will not balance the rotating assembly. L67 rods and pistons weight quiet a bit more than L36 bits and the balancers on both motors are not neutral balance. When I did mine, the shop that did the rotating assembly for me, pointed out the difference in balancers. L67 balancer on L36 crank with L67 Rods, Pistons, and flexplate balanced. L67 on L36 with L36 rods & pistons would not balance out.

How bad, I dunno, I didn't assemble the engine with that combination.

So I wonder if all these dudes over on ClubGP running around with top swaps are shaking their motors apart...must inquire over there...

L36 and L67 balancers are almost identical. The L36 balancer is still really wide, it just doesn't have the ribs in it for the extra belt.

I've had a L67 balancer on my car for 20k miles now. And thats on a bottom end that had 212,000 miles on it when I put the balancer on there...

I dunno...I've been researching this some more and I'm getting mixed messages.

Some say it works fine; others say that L36 and L67 HB'* are NOT balanced the same and thus are NOT interchangeable...not to mention that L36 and L67 app'* apparently also have differently-balanced flywheels (flexplates).

I'm at the point where I'm thinking that a classic top-swap is too much risk for me to take, because of questions over these HB and flywheel balance issues. I can't be shaking my engine or tranny apart, or doing other mechanical things that can't be addressed through tuning.

Now, some kind of bastardization of the zzp SS M90 kit, maybe...

With so many people getting away with it, it can't be that bad I guess. Perhaps the machinist doing mine was just being anal-retentive (works for me ) Or perhaps I just had parts from opposite ends of the tolerance limits.

The whole subject came up because he couldn't find any published specs on how to properly balance a Series II. He worked off what GM did on the original assembly.