I think 0maha posted a video of the solution:

 

That metal puzzle thing is pretty much where I'm at. This is turning into something of a head scratcher.

I disconnected B and C from A, flipped C over (so that the flat part of the clamp is under the pipe) and tried a test fit. Everything is just sitting loose here:



I need a word to refer to the new heatshield (the one that I foolishly let t150vej shame me into buying), so since Paughco calls the little one the "snail", I'm calling the new on the "snake".

In the original install, C was sitting on the left side of A. In this photo, I moved it to the right side of A.

What ends up happening is that if C is on the right side of A, the snail hits it (as in the above pic), and if C is on the left side of A, the snake hits it. Any way you slice it, I've got 10 pounds of **** and a five pound bucket: The total length of snail+clamp+snake is more than the total length of the pipe.

I'm putting all this into an email and sending it off to Paughco. Right now, what I want to know most of all is how they expected all this to go together in the first place. The one thing I'm sure of is that there is no way to fit their pipe AND retain the factory exhaust bracket (#65645-89). When I first bought the header, there was an assortment of hardware with it (although nothing that was an obvious replacement for the factory bracket), but no diagram or instructions. That's how I ended up fabricating my alternate geometry exhaust bracket. IIRC, the B and C that I used came from their original kit. The rest of the stuff is probably in the bottom of a box somewhere, mixed in with a bunch of other stuff, so no clue what's what.

So for the moment, the intent is to figure out how Paughco expected this all to fit together and go from there.

 

Starter design changed in '89, so far as the starter "saddle" bracket, the 65645 -89 differs from the 65645- 85 in the that latter bolts to the starter solenoid and ends up in a slightly different posture. The wide clamp is slightly different on '89 up also. Pipes are identical, it's the mounting position of the saddle bracket (A) that is different. This might explain your need to fab the A bracket in the first place and it's possible Paughos spare parts were designed to work with the pre-'89 A bracket position. The S pipe is much further rearward from the head than the stock design. It has to be that way to make that long curl around. So much for the history lesson....
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At first, looked like the only issue was the tang on clamp C wouldn't let it sit correctly in relation to the pipe. Now, other than tying C and A together, looks like you have it close to what needs to happen.

Both pics, the snail is sitting high above the S pipe like stock parts fit. The standoffs on the backside of the shields (for the hose clamps) should hold every shield far enough away from the pipe to let the shield clear clamp A. But the last photo, the snail looks to be sitting directly on the pipe and that won't hunt.

On the right pipe there is a thick clamp (similar to your A) that holds the pipe to the transmission. That heat shield clears that clamp and the standoffs are the same height. How about your Paugho heat shield on the right side pipe - where it (I assume) clamps to the trans under the trap door? Does that heat shield clear that clamp?

 

Heard back from Paughco.

They sent me this, which would have been helpful five years ago, but alas:

The years are wrong, but Paughco guy "Ian" seems to think it will work anyway. Comes down to eliminating my "A" entirely, and figuring out a "B" that will connect directly from "C" to the starter housing. I'm going to dig through my boneyard. If that Paughco bracket #3 was included in the original headers, I should have it. Or I'm back to fab'ing something up.

The key to this is they're telling me that if I get the clamp (C) in the right place, the heatshields should fit over it.

We'll see. I have my doubts.

"On the right pipe there is a thick clamp (similar to your A) that holds the pipe to the transmission."

I know what clamp you're talking about, but on that pipe, the only heat shield I'm running is the one right up front by the cylinder. The factory shield fit, which made that easy. The chrome on the rest of the pipe has stayed nice, so I've never gone back to add the second shield.

 

Finally got around to buttoning this up.

The moral of the story is "resist the urge to over complicate things". The other moral of the story is "It would be nice if Paughco had included the instructions in the first place".

Turns out, Paughco intended the angle bracket that I used to connect from the P bracket to my custom bracket to connect directly to the starter. Once I figured that out, it was easy. Mostly, anyway. Their bracket was too big and I had to grind a bit off the side to clear the starter.

All said and done, it looks like this:




And with the heat shields installed:




Easy as that.