Modifying headers, what size collector should I use???

I guess this what I get for saying I was trying to be accurate.

They are 1 5/8" schumacher Tri-Y headers.

I belive the plan is to cut them off where the single pipes join for the first time and modify them from there back to fit around the 4 speed linkage, etc...
Then do a similar job with the passenger side to have them look the same. He may be able to keep more on the passenger side and only change the bottom collector section as this side fits with no issues.

All I can say is that for anyone installing headers on a BB 71 Dart with an automatic these pipes fit awsome. Not one single hammer blow or screwdriver jam was required.
But for you 4-speed guys I guess it's not quite that east yet.

Seems a shame to wreck the coatings on them but I need headers and can't afford new ones at this time...

Thanks again,
Butch