This shows a late model primary driven gear with the clutch stack in the fully released position.  The clearance between the tang and the bottom of the slot is about .080".  So, the allowed movement is about .075" (.155" - .080" = .075").

This shows an early model primary driven gear with the clutch stack in the fully released position.  The clearance between the tang and the bottom of the slot is about .100"".  So, the allowed movement is about .030" (.130" - .100" = .030").  That's not very much.  

Since there are a total of 13 plates, there are 26 friction surfaces.  That leaves only about .0012" clearance between friction surfaces.  The clutch won't release.

To use the early model primary driven gear on the 13-plate clutch mod you need to increase pressure disk travel, and increase tang clearance for the innermost drive plate (8).

You can accomplish that by installing an additional washer (7), but I don't think that's a good idea.  It might work, but it could also be very bad if the release plate hits anything.  It might work at first, but as the clutch wears the release plate will drift out closer to the release arm.  You can try it, but I wouldn't add any more washer than necessary to achieve .075" pressure disk travel and .075 tang clearance.  The 2mm washer is too much, a 1mm washer would accomplish what you need to do.  In addition, you should trim the tops of bolts (16) to provide an additional margin of safety.  You MUST do clay checks to confirm adequate clearance.

I personally prefer machining the hard stops and hand working the slots in the primary driven gear.

Since the hard stops in the late model primary driven gear are about .035" higher than the face of the thrust washer, I trimmed them back .030".  It worked good.

And this shows the transfer onto the pressure disk.  Looks like the cast face of the pressure disk is not perfectly square.  I think that's OK.

All of this clutch modification work mandates thorough clearance checks.  Clay checks to verify proper running clearance between the rotating clutch and the clutch cover/release mechanism must be accomplished.  Pressure disk travel checks with a dial indicator are necessary.  If you choose to skip these checks, you do so at your own peril.  This is true regardless of the approach you take, adding a washer or machining the primary driven gear.

Keep us posted.

Then there are the bolts that hold the release plate. when I fit the bolts shown, there are 2mm clearance to the face of the flange on the  sleeve hub, and the clutch is not going to wear that much.