Looking to buy/build 500-600 fwhp 360

I have a 65 Barracuda with a 8 3/4 rear diff, 3.55 posi, A833 "hemi" 4 speed, and 10" tire.
I am new to the world of Mopars, and the car has a low (10k) mile 360.
I will be following this thread closely because I am doing the same thing.
Also read this entire post from beginning to end and had to laugh a bit.
im 60 years old and exactly one year ago I was cruising in a 1000 hp 2015 boosted Mustang. Procharged and 6 speed manual.... ran 9's all day long....so yes old guys like hp and can still drive. Someone wanted it worse than me so now its gone.
Now we are trying my first Mopar. It was something I stumbled on accidently in a storage unit...so I bought it.
A-body 1972 Dodge demon. Currently has a mild 360 in it with 727 and 8 3/4.
Same as the OP $$$ isnt a issue and I want more cubes - 408-412-426 small block with a small to med shot of spray.
600fwhp is the goal as well and will keep it as a auto. I get the manual thing - and enjoy shifting as much as anyone - go to the track occasionally but ultimately Im a street racer for $$$ - lost to many races to the auto guys plus manuals break more ****.
@Lurch59 I have found some builders that sell all forged short blocks or complete engines....but they are not cheap. I also have some good builders close to me - by the way you are only one state away from me :)
As I did the Mustang, my plan is to get the car looking the way I want it, suspension and braking in place, then move to the HP requirements. Here is a few terrible pics of the car as I found it.

1.jpg

3.jpg

6.jpg

8.jpg