Are they credible?

[Shushman]

i need new sills and arches. would these guys be worth buying from?

http://www.carz2.co/bmw-3-e21-57-c.asp

opinions more than welcome.

[Jeroen]

Never know how good they'll fit...

[polov8]

The sills on these cars are in 2 sections, with a joint in line with the back edge of the door. That sill picture shows one continuous piece which is wrong, and makes it tricky to weld to the internal structure behind the rear section. If you did use them, I'd suggest cutting them and using them in 2 parts to repair your sills in the way they were designed.