Hi again.
A lot would depend on how much of the work you would be doing yourself.If you snatch the motor out and take it directly to the machine shop that would actually be doing the work,instead of taking the car to a shop and have them snatch the motor out and take it to that same machine shop,and tell them what it is that you would like to get out of the motor and work out your plan of attack directly with them you should be able to stay within that price range.That would be with you being the one to reinstall the motor,buy the top loader and a new clutch and install them.Their are always the little 'while I'm at its' that will nickel and dime you to death,like 'while I'm at it,I guess I ought to go ahead and get new motor mounts.',and 'while I'm at it,I guess I ought to go ahead and get one of those cool looking 7 quart oil pans.'etc,.etc....sub-frame connectors,rear sway bar,Shelby drop,3.89 rear end,new 15X8 wheels for the back and ,of course,the matching 15X5 wheels for the front,the list goes on and on and on and on and....But,throwing 6K at a running, driving V8 4bbl ought to do some pretty serious damage.Hope that helps.
289 A code ? 
You'll be needing a different cam,intake and carb,roller rockers,some free breathing headers and the trusty MSD ignition system.You will also probably need to have the heads ported.Maybe a stroker type crank with some different pistons to get the compression up a little.If you do all of that it will probably grenade the tranny in fairly short order.Then you can go ahead and get a 4-speed top loader,which is pretty much bullet-proof.It's also easy to overlook the fact that a car that launches better also needs to be able to stop better.You'll be needing some front disc brakes while you're at it.Hope that helps.
