99% of small block 6pks run well with the mixture screws in the outboards 1/4 , 1/2 turn out.Beyond that they can go rich real quick.If the outboards are rich you will have trouble with the center adjustment.2 1/2 turns on the center is a place to start once you have the correct idle rpm and ignition timing..Also,as some call them rebuild kits,you get nothing more than new accelerator pump,needle/seat,gaskets and clips.If you presently have no leaks,have throttle response,and you can adjust the float level and have no flooding,you have accomplished nothing.The acception would be an original carb that still has the old cork metering plate gasket in place and after 40+ years I doubt there are many of those around.
Now,if the metering plates have been modified and major jetting changes have been made then it is a whole new can of worms.