If you have stripped a number of B-Screws, you can find replacements by searching for the following specifications:
Cylinder Head Connector, Confirmat, Hex Socket, 4 mm, Bronzed, length 50 mm, Ø 13 mm (Supplier Website)
Or: CONFIRMAT ST BZD 13MM HEX 4 7X50
A 4mm hexagonal drill bit is recommended. A 3/16" hexagonal drill bit will also work if you do not have access to a metric bit.
Do not use more than 5lbs/ft of torque when installing these screws, or you may risk stripping them.
Replacement Rack Rails
3U Rack Ears
https://www.reliablehardware.com/pairrackrailsfullholepre-cut3space525incheslong.aspx
Rack Ear Specs
· 1/8'' Thick Steel (11 ga.)
· 1.55'' x .68'' x 5.25'' Long
· Tapped with 10-32 Threads
· Black Powder Coat Finish