Bang for the buck.

Turbo anything is usually the best answer.
If you are like me, and no longer have access to tools and equipment I had before retirement, or fab skills are lacking......?
For me, my cheapest/easiest way to 750hp would be an all forged 400 stroker kit, cheap aluminum heads, and a nitrous kit. Since a real 550 crank hp would get my car where I want it to be (low 10's) I would forget ( maybe) the nitrous.
Could probably make 650 with a stock stroke 440, good heads, good internals, and a 200 shot.
Tune would be crucial for a decent lifespan.