If you found yourself falling into some cash, you could shop around for some better heads like 781's or 042's which are some pretty good oval ports and can support 500+ HP, you would get yourself some .400 longer connecting rods, and some standard 427 pistons that are two valve relief flat tops. This eliminates tons of weight from the rotating assembly. The 427T cranks are forged so I would reuse that.
But if you fell into a few hundred extra dollars on top of that. You could buy a cheap 4.25" stroker crank, along with the +.400 rods and .060 over stroker pistons, you would have a 496 CI big block. Stick a nasty cam in it, a 850-950 cfm carb and a big intake on it and you will have more power than most sane people can handle on the street. You would still only be into it for around 5000.00 As long as you didn't try to spin it past 6500 RPM it would last plenty.
I have personally done this last step and made over 550hp on pump gas with an 850 carb.