Help w/Grafting in an Early Sliding Ragtop

[mattsvdub]

Hey guys..
I'm getting ready to do a 58-63 Ragtop graft on a 67 Bug and had a couple questions.
How critical is it to have those corner and side support pieces on the underside of the clip that your welding in?
(The guy I got this clip from who shall remain nameless due to I'm tired of bitching about poor descriptions.)
The top was cut fairly close to the actual cutout so I don't have allot of room to work with.. If you don't know what I'm talking about I'll see what I can do for photos..
Where is the best place to get replacement pieces for the mechanism itself? You know those little nylon rollers and such...
Thanks for any info and light on this subject...