I have a 67 coupe with a 289 and in the process of converting the factory single exhaust to duals.
I bought a full aluminumized dual exhaust system and not sure how to mount the hangers at the intermediate pipe/muffler point.
It has these 2 plates with 2 bolts protruding out that the hangers mount to.
How do I mount these plates to the floor pan?
Do I drill 2 holes through the floor pans and feed them from the inside or screw them to the bottom of the floor pan from the outside?

Any help or advice.........?
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Still waiting for reply........

 

I'd think you'd weld them on. Can you take pics?

 

pics would be great. in anhy case make sure to have the driver side pipe well clear of the brake line to rear axle

 

no, the 65-69 muffler hanger stud plate was mounted from the inside, and screwed in place.