Hi and welcome.

There are basically two standards for Tune-O-Matic style bridges, the USA/imperial one and the Asian/metric one. The kits use the Asian/metric one.

Had you a bridge make in mind? I've got some of the TonePros metric bridges, but also just got one of these https://www.northwestguitars.co.uk/t...aul-sg-es-dot/ for my GSM-1 build, and that's a decent bit of kit, just lacking the locking grub screws of the TonePros (which are modified Gotoh units). That link has a dimension picture which should be correct for the kit. I'd always suggest a Nashville style T-O-M over an ABR-1 style one unless you are trying to be period correct, but then the kits are drilled for post bush inserts (11.5mm hole for 12mm insert diameter inc. the splines), snot screwed posts like an original Gibson ABR-1 (though Gibson now use bush inserts for their ABR bridges).