There are a couple of things to consider. In order to get the motor to make the power you are after, you are probably looking at a max RPM of 6500-7000 RPM. That being the case, I would recommned getting an aftermarket rotating assembly. If you end up doing that, I would recommend building a 496. Once you get into aftermarket parts, it really does not cost much more to stroke it. If you are after something a little less expensive, I would look at using as much of your rotating assembly as you can and using a set of ported 049 or 781 heads. With a mid 240's at .050 ~.600 lift cam You could make around 550-600 hp @ 6000-6300 RPM with that setup. If you went with the 496, I would recommend the 315cc AFR heads and a solid roller cam in the mid 250's at .050 duration ~.650 lift. With that setup and 10.5:1 compression, I think you would be in the 700-750 range at ~6500-6700 RPM.
Here is a motor I just built and what power it should make:
496
9.5:1
248 254 @.050 ~.600 lift solid flat tappet cam
victor jr port matched to heads
fully ported oval 049 heads with 2.19 1.88 valves.
This motor should be around 600 hp/600 ft lbs pretty easily
This is a motor my friend built:
461
9.5:1
242 248 @ .050 .600 lift hyd roller cam
Victor Jr intake ported
cleaned up 781 oval heads 2.19 1.88 valves
This motor made 560 hp @6100 RPM/560 ft lbs with 20w50 oil on an engine dyno.
These show what the AFR 315cc heads are capeable of:
512 ci
~9:1 (would be a better match with 10.5:1)
254 260 @.050 .660 lift solid roller cam
victor jr intake
AFR 315cc heads
741 hp @ 6400 RPM 690 ft lbs @ 5100 RPM
http://airflowresearch.com/articles/article052/A-P4.htm
496 cid
10.4:1
255 265 @.050 .629 .629 lift hyd roller cam
holley single plane intake
AFR 315cc heads
Fuel injected
728 hp @ 6800 RPM 645 ft lbs @ 5400 RPM
http://airflowresearch.com/articles/article071/A-P1.htm
My motor is not in my car, so I dont know what it will do in the 1/4, but I have heard of combinations similar to mine in novas running really low 11's on drag radials and full exhaust
Adam