[sixtysevenGTconv]

IIRC 20 yrs ago when I did mine at a custom shop, found mounting distance info in 67 shop manual, as to how far they should stick out. My NOS rolled tips I bought of friend the had long time, not going to use.
Noting my pic view of underneath showing my orig Ford "shipping brkt" that I still have. They were longer for factory dual exhaust stangs (the S&K code cars). Dealers were suppose to remove and send back to factory, many didn't.

 

[sixtysevenGTconv]

My 67 a factory dual exhaust car. Had custom shop install to shop manual specs, (can't find mine either, but did shop manual down load somewhere). I think out just enough.

 

[sixtysevenGTconv]

That looks close to the blue picture in my last post. I'll do something close to that. I notice on yours that they're not tucked up in the valance like the green & yellow. Do you know if they were tucked tightly from factory, or more like yours and the blue pic?

I'll have to see if I can my ref pics or book. I'd believe spec was to have them not only a spec'd distance out but also equal spacing all around them. Centered in the opening.

 

[sixtysevenGTconv]

I found Ford Shop manual pdf on my pc. If I can't get it to copy to hear, it's on page 616 in mainual. Gives equal clearance arond tips to valance as I mentioned earlier.

IF I read correct, has 1 1/4" - 1 1/2" clearance out.
Then 5/8" - 3/8" clearance tips to valance.
IF I read correctly

 

[sixtysevenGTconv]

I think distance coming beyond valance is fine.
The back of my mine initially I was worried about tips in too far, getting exhaust fumes in trunk..

 

[sixtysevenGTconv]

Not sure what Ford‘s measurements were, but these are mine. From NPD fwiw.
Troy
View attachment 949483

"Not sure of Ford's"
I posted it above. My diag pic from 1967 Ford Shop manual!