360 La build ideas!

Why? Would be my first question. That's a lot of power your looking at 600 gross hp.
Just the chassis and brake work needed for that power level would probably kill your budget. Have you ever even drove cars close to that power to weight level. A 5.0 liter mustangs used to be the hot ticket and barely made over 200 hp.

Natural aspirated engine your looking at heads that can flow well over 300 cfms and lots of $$$$ to used them. A 500 cid big block would be the best choice for that. But to be more budget friendly you'll need some kind of power adder, cheapest would be a 400 hp 360 with 200 hp of Nos