351 or 460 high RPM

So I would think you do not want a lot of weight over the nose so my vote would be a stroked 8.2 deck motor but if you a set on using what you have on hand then the 351W with aluminum heads, intake(s), and a much other light weight parts you can put on it.

What exactly are you considering high rpm?
This could get really expensive.

I'd say the 460 is out just based on weight alone.

What's the budget?

Your goals are admirable, but since you aren't rich, i highly doubt 600rwhp and 8000rpm NA are attainable. You can certainly forget about 800hp.

My guess is that 450rwhp@6500rpm is a 10k build these days all motor and with a 351 based block and you still could very well come up short.

While i'm not all about coytote swaps, i bet it in this case it saves you money and gives more reliability.

Everything is more expensive with the 460. You can build 393 that can put out some decent power. You'd actually save money by selling the 351 and the 460 to buy a Dart block. Machining is machining. A turbo charged zero balanced Dart block can produce the power and handle it. It would also allow you to use a cam that has a lower lift profile than a NA radical camshaft. Either way it's going to cost some money. In your case, the Dart block turbo might get you where you want with a little more left on the table.

The real issue is RPM. Windsor engines don't tend to like it. Any engine you build would have to be zero balanced at a machine shop. It would be best to go with a Ed Curtis or other custom grind with the camshaft. They would determine what rockers, springs, and push rods you need. You'd need the heads and intake flow numbers to match the RPM you're going for. RPM is brutal on push rod engines. Without precise clearances and finishes it could end up really bad. The oil pathways will also need modification. For prolonged higher RPMs about 6k you'll need to get the oil back to the pan as fast as possible. For the goal you want you'll need an aftermarket block, aluminum heads, and a power adder. There's no cheap way to make a 6- 800hp Windsor engine. The 460 can make good power NA but it takes parts, modifications, and everything to support it. Either way you're looking at a realistic total of atleast 30k+ to get where you want to be. The engine alone would be about half of that. You'll need a transmission, rear end, suspension, and braking stuff.

I have over 30k in my car and it's just a 331 with aluminum heads, intake, h beam rods, and everything internally upgraded. My engine doesn't make 500hp NA. I've got about 5k in the transmission and driveline. A few more in suspension stuff. Not even bringing up the cooling system, fuel system, and engine control.

I hate to say it but it would be cheaper to turbo a LS 5.3L and run that.