So I'm using the 3.8 stud kit #123-4003 but being told they're too long sounds strange to me because in order to see if the studs would be too long in a way that the nut would potentially bottom out or run out of threads I first screwed them in. I then measured the depth of the holes in the head and then marked on the studs where they would begin sticking through the head and seemed that there were plenty of threads there left before the nut would bottom out. There were some that were a little closer to the bottom of the threads than the others and those were the ones I was going to use double washers on. Would I need to get the 123-4001 kit for the production block, I wanna say my 291 block is from 1983 but not 100% sure on that.Yes, you need sealant. On, your deck surface (and your heads deck surface) bevel the shit out of the hole to spread the clamp load out and away from the threads themselves.
Also use your head gasket as a template to drill steam holes in your heads to let the air pockets out of your siamesed bore block.
The 3.8 bolt kit won't work. The studs will be too long. You need the correct ones for your block that doesn't have the countersunk holes. I think ARP lists it for the 8 bolt stage 1 block (it's been a while since I bought mine)