Almost all of the screws used in the Williams/Williams by Bachmann diesels are listed on pages 6 and 7 of the 'O/Williams' "Universal Parts" lisings. There's not a lot of variation in the screws used on different diesel locos:
https://estore.bachmanntrains.com/index.php?main_page=index&cPath=77_219&sort=20a&page=6
https://estore.bachmanntrains.com/index.php?main_page=index&cPath=77_219&sort=20a&page=7
All of the screws are metric. The only real difference I ran into when things switched to 'Williams by Bachmann' is for some reason the pilot mounting screw on the front truck was changed from 3mm to 3.5mm
Len
https://estore.bachmanntrains.com/index.php?main_page=index&cPath=77_219&sort=20a&page=6
https://estore.bachmanntrains.com/index.php?main_page=index&cPath=77_219&sort=20a&page=7
All of the screws are metric. The only real difference I ran into when things switched to 'Williams by Bachmann' is for some reason the pilot mounting screw on the front truck was changed from 3mm to 3.5mm
Len