Due to overheating problems in my '74 454, I'm about to install an aluminum high-flow water pump, as well as spring-reinforced radiator hoses. I've been told I should also install a high-flow thermostat. Is this necessary or recommended, and will I need to also get a different thermostat housing? Any recommendations? The car only seems to overheat at high rpm. Thanks.

The thermostat will fit with your existing housing. It is just made to open a bit farther than "normal", and some have slightly larger "pellets"(centers).
If you are only having an overheat issue at higher rpms, I would think you might be better off looking into your radiator, tho a corroded/non-functioning WP would cause the same symptom.

As Joel said, have that radiator tended to. Get it fully flushed out and pressure tested. While you're at it, have the radiator cap pressure tested as well. It's often overlooked and can cause overheating and coolant loss problems.

Pour in a bottle of Water Wetter when you're done as well.

The overheating at higher rpm's is classic symptom of a bad lower radiator hose.

mine blew top hose off,,am about to replace hose- &-thermostat , but what is water wetter? who sells it,

Water Wetter is a chemical that coats the internal parts of the cooling system and allows faster heat transfer from the metals to the coolant. Using it won't really keep a car from overheating if there is a problem, outside of maybe delaying the overheating a bit, but primarily will make the engine run a bit cooler under normal conditions..

You can by it at Pep Boys, Auto Zone, etc. It costs about $8 a bottle. Supposedly it's more efficient added to pure water, but also works fine mixed with glycol coolant.

thanks.i`ll check it out