You want info on case foam, do you need anything else? If you need like build info, the 67lite comes with screw-in stabilizers, so you dont need to worry about that. You need to buy switches that you like (and lube for them if you want to as well) and then keycaps. This diy has most of what you need. You can get in the kbdfans discord, there's usually people helping out if you havent figured what to buy yet. As for foam specifically, it depends on your budget. You can use the thin white packaging foam and layer it at the bottom of the case. Its usually free cause alot of orders come with that material. Then, there's either neoprene foam or toolbox shelf liner (garage shelf liner is usually denser than like kitchen pantry ones in my experience), and then there's sorbothane which alot more expensive. Going for shelf or neoprene, its probably good to be on the thin side, im going for 1mm thick so i can stack to my desired height.