Here's a combo that works very well for me on a 496 with AC:

- MP High volume water pump with anti-cavitation plate driven about 7% above crank speed
- MP aluminum housing
- 26" aluminum top tank radiator, 2" thick. Its a Mancini "Muscle Car" radiator
- Matching shroud
- 180 degree high flow stat. Originally Mr Gasket which worked (apparantly many don't) and now a Milodon stat only because I was nervous about the Mr gasket
- MP clutch fan kit with 5 blade "low drag" fan. I have a 7 blade as backup but haven't needed it

With the car moving, it always runs right up against the 180 degree stat. It actually ran 175 with the Mr gasket because it opened a little early. With the car parked and idling on a hot day with AC running it will creep up to 205 or so after 10-15 min.

I'll suggest you look at the water pump first and radiator second. Check pulley ratios. The high volume pump slightly overdriven seems to work really well. MP pumps are still available but spendy. If I bought another I'd probably buy a Mancini high volume.

On the radiator, you didn't comment on age or condition. Usually, hot running at speed is a sign of a plugged or inadequate radiator. A clean full depth (ie 2" or more) 3 core should do it but for some reason yours isn't. Some aftermarket 3 core rads are really thin. If its old or plugged or thin you may need a better radiator.

Also the tuneup matters. Mechanical + vacuum advance to get you in the 35-50 degree advance range while cruising helps the engine run efficiently and cool. A good cooling system should still be able to overcome a not perfect tuneup but every little bit matters.