I couldn't find it on their website, but I'm pretty sure Classic Auto Air makes a 6 channel factory replacement condenser that's more efficient than the original or standard replacement 3 channel design. It's available through NPD and critical IMO if you're switching to R134A. Since your car was a factory AC car, and you already have all of the under dash pieces, I would do as spade 33 suggested and send the entire plenum out for rebuild. Then you can replace the AC hoses, condenser, dryer and expansion valve with all new repro stuff, and it will use the factory routing and install locations. To finish the modernization, use a mid 80s Ford compressor from an F150 with a 302/351W rotated 90* on it's side. The factory discharge hose will hook right up. A factory replacement sight glass hose will go from the dryer to the firewall with the original routing. Now the 2 critical parts to this upgrade are fabricating a mount for the compressor and making an adapter for the suction hose that goes to the condenser. The mount is really not that hard. Use 3 pieces of flat plate, 2 identical pieces with holes to mount the compressor, and slots in the bottom piece that will mount to the factory bracket that bolts to the head. After you have everything lined up so that belt aligns properly, tack weld nuts in place on the bottom of your fabricated AC compressor bracket. You can use either R12 (replacement) or R134A.
Just a bit of useless trivia (that I can't confirm btw) I was told by a retired factory York distributor that all of the York and Tecumseh automotive compressors were actually made in Japan. Because WWII was still fresh in everyone's mind, The American Auto manufacturers couldn't install a Japanese sourced component in the early 60's, so they went through York and Tecumseh, who spec'd them for American cars and put their names on them.
Sorry man! Well at least it's money well spent! 
