360 Bellhousing bolt size

Anyone have the length for the bellhousing bolts? I know they’re 3/8 but when I get my engine mated to the trans I don’t want to get in the predicament of not having the appropriate bolts to use. I don’t have any bolts either since the engine and trans were not mated prior so I need to get some. It’s a 360 and 904 trans. Thanks guys.