Build/Repair checks are extended, yes. For the Sheriff mods, you're looking at:
- Firing Selection Change; Threshold 10
- Powered Folding Stock; 8
- Increased Cylinder; 10; this is the one where you're taking the Insufficient Tools penalty, the others are as normal
- Underbarrel Weight; 6; for this one you're actually one step UP from the minimum required tools
The Personalized Grip requires Artisan, so I'll have to get that one done by contacts.
And if Chrona wants mods done for Three-Star's new rifle, he should probably bring that up.