LS6 to LS7, LSA, or LS9

[Genros]

Hello all
My 69 camaro is currently running a ls6. I'm wanting more power and understand the ls6 is somewhat limited. What would be the most direct swap? The ls7, las or ls9. I'm not interested in doing a swap twice nor do I want to spend money unwisely. I'm aiming for 650ish at the wheels. If i come close I'm happy. If I swap in the ls7 a sc would be in the future. Help

Add, I'm running heights subframe and coin overs and rear four link