those heads are drilled for 1/2 studs and the 302 block is 7/16 thread so you have to get 7/16 studs and use a bushing that goes in the head iam not sure of the part number, i would just call AFR they are pretty good there and will give you a part #
you don't have to use studs, bolts will work to. size of the bolts/studs depends on the block you are using. 302 you use the 7/16" size. 351 you use 1/2". now if you have a 302, and heads are drilled for 1/2", then you will need to also order what is called(or at least I call it) is "head bolt bushings." these will go in the heads just before you put the bolt/nut in/on the block. i know edelbrock and TFS offer these seperatly, just have to get a part number or call them.