The most important item for performance is the torque converter. I don't care how much you do to anything else the converter is the most bang for the buck. 3500 stall no less.. The 2500 low stall converters are for plow trucks and RV's . While the engine is out that and a front seal would be first on the list.
Ya Ya. Hi stall is OK for more of a track car. With the stated 3.23 gears a 3500 stall converter will always be "slipping" creating heat and poor fuel economy.
With a short duration cam, a slight bump in compression, a 4 barrel intake of 2 plane design and headers, a lot of stall is not required to make a good street driver.
Now a lockup converter can change that, but most of the older transmissions do not have that option.
