These channel guides are for 51-54 but you may find them here for your 49. I think the earlier models had window guidies that are wider.
http://www.classicparts.com/Door-Rubber/products/4/

also try JimCarter or American Classic


1937 Chevy Pickup
In the Gallery
1952 Chevy Panel
In the Gallery
More photos
1950 Chevy Coupe
Pictures!

I'd rather walk and carry a Chevy hub cap than ride in a Ferd.
I can explain it to you, but I can't understand it for you smile