Not sure if there is a cheaper way so can't help there, but if you go with vintage air its a good unit. I used a vintage air unit and reversed it in my 69, had to modify the brackets a little to mount the unit. As Shaun said it will depend on how your firewall was done, i needed to get the recess in the firewall enlarged as mine was only just large enough for the heater and the vintage air unit is longer, but the car was stripped and getting a lot of body work done so this wasn't much more at the time.
I didn't use any of the plumbing that came in the kit (used everything else though) and had it all custom plumbed. All four pipes come out of the unit then make a 90deg bend to go through the firewall, emerging under the guard. From there the heater lines again turn 90deg through the apron and enter the engine bay just under the LH bonnet hinge and my air con lines run all the way forward under the guard.
The vintage air unit works really well, even in a Darwin summer the car is nice and cool, but the plumbing wasn't cheap.
Good luck.
