69 barracuda 340 or 383 exhaust tip mounting

They look like this:

307-H Mopar A-body Exhaust Tips Hangers

1968 Dodge Parts | MA2483 | 1968-74 Mopar A-Body Exhaust Tip Hangers Pair | Classic Industries

and bolt to the inside of the frame rail as it extends tot he rear valence. There should be a pair of hole is each rail to accept a U nut.