DONT SPEND ANOTHER CENT UNTIL YOU FIGURE OUT WHAT YOU WANT!
Make power on a budget usually doesnt happen. If you are planning on rering-regasket, figure on $800-$1000 rebuilt as stock. If you want to do any performance upgrades, $1500-2000 by the time youre done for a very mild build. If you want to make power and dont get carried away, $3500-5000. Be honest, what do you want to accomplish here?
ADVICE:
Decide everything before you spend a penny. What youre buying, price, etc then post it here for advise. What youre doing in this thread is great, just dont buy the parts until you have the whole combo worked out. Some of it might change, and money goes out very fast on builds.
BUILD IT FOR TORQUE!, Torque moves you, and you will like it better for a mild build.
1) Throw away your 650cfm carb, dont care what it is, its not enough. You need a 750, i promise it will be better.
2) HEADS HEADS HEADS HEADS HEADS! The power is in the heads. If you can afford to go to $5k, get a set of edelbrock heads, and the highest lift cam with the smallest duration you can find, and throw it on and go. If youre paying someone to port your heads, buy a set of eddy's, its more bang for your buck, and a better investment if you decide to sell later.
3) Compression helps ALOT. Aim for 9.5-1, you can still run pump gas. Can go all the way to 10.5-11:1 if you go with eddy's.
4) Torque converter! If youre running an auto, get a nice converter or you will never realize the power.
5) Gearing, dont go crazy with it, these engines made good torque. 3.08 is very good, 3.42 is perfect, 3.73 if youre brave, but highway isnt nice. These engines like to overheat.
I wanna spend around 1500 the things you said you would get you wouldnt change the pistons??
Dont get carried away, because you can probably spend the same money on a 455 and have way more power. If it were me, id rering, regasket with the highest lift shortest duration cam i could find, headers, torque converter, aluminum intake and a 750cfm carb, and call it a day.