I think "streetability" is very important to one's enjoyment of a Replica. I have a custom built stroked Olthoff Windsor, not a 460 engine, with a dual plane, Pro Holley HP, a hot Motorsports cam, etc.
But i can trundle around in my .68 fifth gear at 1000 rpm, without protest or stumble, and accelerate from this speed, about 35 mph, very smoothly. I was showing this to a prospective purchaser recently, i had him slow to an even 1000 rpm, then accelerate. He was impressed.
Yet my engine's dyno curve shows the power curve still going up until right at 6000 rpm, too. I have somewhere between 460 and 480 hp, depending on the ambiant temps and such.
But one does have to accept some compromises Vs. all-out high RPM power. I know some guys with similar engines with single plane manifolds, and their engines are not nearly so happy at the low rpm my engine loafs along at. What it means is the difference in rolling along in traffic at 1000-15000 rpm, restful and peaceful-like, or running in a lower gear with all that noise and wear, which of course i chose to do sometimes for fun.
It also means i can cruise the back roads in fifth at any speed, without having to constantly shift to keep my engine in some narrower powerband. Remember, it is torque that accelerates the car.
Besides, i have heard that the valvespring pressure on the higher horsepower big blocks are not meant for any reasonable street durability. It is a drag race motor, not really meant for street use.
At now over 50K miles, my motor is strong, leak-free, and runs with the same power it always had. All I have done is change my
oil and filter appropriately.
I think there is a realistic limit of how much power a driver can (safely) use in one of these cars out on the street. I drove up and back to Charlotte lalst night, just to get out under the stars. About 50 miles. I did not have any opportunity to fully thottle my engine, even when leaving several interstate rest-stops. I have many hundreds of miles on road race courses, and over 60 quarter mile runs. These are pretty much the only time's i actually use all my engine's power, as i am ever vigilant of the unforgiving nature of my car, if i am ever even momentarily careless.
I thing one better be a pro-ability driver if he plans to actually frequently use 500+ hp in one of these cars. I am not.