Are you planning on doing an entire rebuild or are you just looking for some things you could do to what you already have? If you're not planning on doing an entire rebuild ( that means everything taken apart, cleaned, machine work, everything ) that's OK as long as the engine is in good shape. This is what I would do;
1) Get a set of older 350 heads ( 5,6,7, or 7a ). These will give you a nice boost in compression. If you were to do an entire rebuild, then I would get a set of readily available flat-top pistons and keep your 8 heads. You'd end up with about the same CR ( around 9:1 or a bit more ).
2) Get a good valvejob done and clean up the bowls a little. You can get bigger valves too if you want but you don't need them. You would probably be better off going to an adjustable valve train too like the Comp roller tip rockers.
3) Get in touch with an Olds engine builder and them recommend you a good cam. Can't really recommend one until you know the specifics of everything else, but assuming you had good gearing and the proper converter, something like the Lunati 217/221 cam seems nice.
4) Headers and 2.5" true dual exhaust. Add H or X pipe if you wish.
5) Keep your stock Qjet and just rejet/tune it.
6) Recurve your current HEI distributor.
7) Edelbrock Performer RPM intake manifold. If hood clearance is an issue, you could get away with running a regular Performer intake and still meet your goals.
With all that said, if you want your car to really move ( you only have a 350 and your car is very heavy ), then you need better gears for sure. The bigger you go on the gears though, the crappier it gets when cruising at higher speeds. Some people are OK with big gears on the street like that. I'm not one of those guys. Personally, I would go with a 2004r transmission so you can run good gears ( like 3.73 ) and have much better streetability due to the overdrive.
For comparrison, look at the engine in my sig. It's a pitifull little thing. It's only putting out about 280 HP. I ran a 13.83 @ 96.85 mph and though your car weighs a couple hundred pounds more than mine, your engine would put out noticably more power than mine.
