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Here's the screw I used for the belt clip. Fits like a glove and it comes in various lengths
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I would highlyrecommend buying this pcb designed for the ls6 box, it makes life a lot easier
https://www.etsy.com/listing/637784550/control-box-pcb-kit-for-korbanth-parks?ref=shop_home_active_2&crt=1