I got the Gerson green channels for my 55. They make them quite year specific if you want your car correct. They fit great with the right profile, and have the proper heater vent in almost the exact spot. That's my only complaint is the vent hole is around an 1/8" too low and 1/4" too far forward. And the mesh in the hole is a bit finer. But once they are both in you couldn't tell the difference.
A little pricy but you only want to do this kind of surgery once. The amount of work is the same so to save a couple hundred on the channels and then have a car that doesn't have the proper sill profile is IMHO not worth the difference. Most people couldn't tell but it could be a deal breaker if you were to sell the car
Of course the year makes a difference in whether this matters to you. If your 50's bug is an Oval, I wouldn't think of using anything but the Year correct channels. So I guess that would be the Gerson ones. If it is a 58 or later I don't think the difference between the cheaper generic Heater channels from CIP is as much of an issue.
I got them from Concept 1 in Calgary.
http://store.concept1.ca/store/ $333 each and $60 shipping. Arrived in 3 days from Calgary was quite impressed. Ill upload some pics later to see them in the car.
