I would figure what gas you are going to run your engine on and go from there.
Because your 1000hp build wasnt going to run on pumpgas - well not for long anyway.
I did a 2 bolt mains 454 with cast crank, stock rods, a CompCams blower cam plus some TRW 7.6:1 blower pistons and fitted a 671 on top and then went flash with a set of second hand Bowtie alloy heads. Only ran about 6lbs and made 627 hp.
Strangely, the bottom end never let me down but the used alloy heads did.
I think twin turbos are a great idea, but if I were you I would start with a good block and get some forged internals - rods crank & pistons, and build up from there. You wont see 1000hp unless you spend serious money, but you can get a start point that you can lean on, and learn from there.
All the best with your SBC learning experience