Gl1200 different yrs used in a transplant

[made2care]

So the bike I’m transplanting a new engine to is an 84 gl1200 , think it’s an interstate. The donor engine is an 86 gl1200 but.... I noticed a difference on the back of the 84 ( the part with a green x) Can someone identify this and it looks like I can still use the donor engine as the mounting points are the same. If not, let me know.
Thanks

[lcdrjoe]

Someone far more knowledgable than me will verify this, but it looks like the 84 pulse generator. Maybe you can wire it up, I'm not sure. Here's a pic from the Haynes manual:

[made2care]

I think you are correct. Now I’m discovering that the starter is larger on the 86 I think therefore one engine/ frame mount might not line up.

[Shadowjack]

That is indeed the pulse generator on the 84 in the rear. Not quite the same, but I put an 85 engine in a 75 frame and the mounts all lined up, although just a bit of grinding was required on one of the lower brackets (I forget which side), and there was a pry bar involved. But who knows if the frame was not warped after 40 years.
Be aware that the pulse generators are different between 84 and the other years, not only the wire length but also the resistance values. The ignition amplifiers are also different, to match. I'm not sure if they can be swapped without problems or not. They're getting hard to find, though. And expensive.
Study the neutral switch wiring. An Interstate has wires for neutral, fourth, and fifth. The two top gears turn on vacuum advance. An Aspencade also has wires for first, second, and third, because it has the gear indicator on the dash. Can't remember if the plugs will just work or not.

[made2care]

Let me explain what’s going on. The 84 I just purchased has a head with a broken spark plug. On top of that the po welded something onto the plug so basically I can’t extract the plug. I had an extra engine but it’s an 86 and looks like it cannot be a simple swap into the 84. I’m assuming the 86 head cannot be used on the 84 either. If so... please let me know.
With all that being said I will try to find an 84 head .

[Bike...and Dennis]

Actually, I think the heads will swap.

[made2care]

Okay. I’m going to remove the head from my donor engine- 86 and see if I can use it.
Thanks