Hey bud, glad you found us...
The parts I make replace the Nylon holders that the head light adjuster screws screw into. After 30 years, they start to split and break, so I came up with a permanent steel replacement.
As for changing from square to round, your best bet is to find a donor and get the entire buckets. Then send me a PM and we'll hook you up with adjusters before you install them, then you can adjust them and forget them.