The output of the compressor muffler goes to the condenser and receiver/drier at the front of the car. The condenser mounts to the front of the core support. There are 2 mounting brackets that are bolted to the condenser and then the brackets bolt to the core support. I think 69s use a different condenser and brackets than the 67-68 setup.
If you are converting to R134a and are not concerned with originality, you may want to consider getting a modern parallel flow condenser. Parallel flow condensers are more efficient and the system will work better when using R134a, but will probably need some mounting bracket and hose connection fabrication.
Pictures 1 and 2 show the driver's side condenser mount.
Pictures 3, 4, and 5 show the passenger side mount. In picture 3 the bracket is partly hidden behind the hose between the condenser and the receiver/drier. Picture 5 is a close up of the bracket to condenser mounting using a U-clip.
Driver's condenser mount
Driver's condenser mount
Passenger side condenser mount
Passenger side condenser mount and receiver/drier mounting bracket