The blower will be the limiting factor; I doubt it'll reach 500 rwhp n/a - think about it - that's over 1.72 fwhp/ci, in a (relatively) low compression, low rpm motor. I'd expect that combo to peak around 6,400 rpm n/a; the blower will likely give you a little more rpm. I do think that 650 rwhp is possible with that combo, esp through a stick.
'84 LTD LX - 9.83 at 140.09. Whippled 365 SBF with a glide and 3.08 gears. Driven to and from the track 60 miles without even changing tire pressure.