If you search this topic there has been much discussion about it. In my personnal experiance working in a restoration shop, I have installed both. The Vintage system twice several years ago-so things may be different now-compared to the Classic system, I found the Vintage system very difficult to install, brackets did not line up or reach mounting points shown in the instructions...and on the two occassions I called Vintage "tech support" I got very little help or resolution. I have installed 6 or more Classic perfect fit systems and have had little to no problems, and great tech support. It fits where it says it should fit, and the instructions are decent. My supervisor ordered one for his 67 Mustang I am assisting with. He opted for the electronic controls which will be a HUGE improvement over the stupid cables...worth every cent.
I have posted this option a few times as well. If you were ever to consider a March serpintine conversion, (expensive) you can flip the condensor 180 degrees and run the lines under the battery tray to the passenger side mounted compressor-under the alternator-very slick. In fact, I called Classic tech last week for my supervisor and they RMA'ed my supervisors compressor for the one that fits the March bracket without batting an eye. No problem! was the response. And shipped for free. Only cost to ship the one back to exchange it.
One last Classic kit tip-the firewall plate can be flipped and put on the lines from the inside power pak unit (evaporator and fan) with grommets, and then the plate fits the firewall hole from the inside. This takes some work and is a bit of a pain, but also looks VERY clean and professional. You need to epoxy some nuts to the inside of the plate and drill the holes out and work 4 lines through 4 grommets at the same time...then you can put some new bolts in all four holes in the stock firewall hole into the plate. One of the holes is a mounting point, the others just get snugged tight for show.
Hope that helps.
