sorry for late reply

to change the crowbar as the default weapon to another weapon is defined in the classes in the game.

to change that, you need to actually change the configuration of what the classes themselves give.

(assuming you have the gamemode folder)
GarrysMod > garrysmod > gamemodes > laststand > gamemode > player_class

under the "function PLAYER:Loadout()"
you are able to add, modify, or remove current loadouts.

if you don't have the gamemode folder, you can use some workshop downloader website but some can be pretty sketch. you could alternatively request the owners of the addon to give one to you.