Daytona overheating conundrum-help!

Thanks everyone for really fantastic ideas and information, sorry I have been away from the computer for a week plus. I will not be able to work on my Daytona most likely for several weeks, but I will revert when I have done more diagnostics.
However, since this problems has been slowly progressing over the past few years I am near certain I will have nicely clogged water ports in the heads.

I am thinking I can use a doppler probe to ascertain water flow and relative velocity in the hoses

So the next obvious question is, who should rebuild it without costing an arm and a leg, just an arm would be tolerable possibly. I can rebuild a basic engine but 365 motor experience would be very helpful. Unfortunately my "guru" passed away this past spring so I am a bit adrift when it comes to old Ferrari help!

Ken

 

Here is an update to my overheating problem. I finally had some time to trouble shoot the car. Here is what I did, disassembled the water pump, could not see any problems, then I rigged a garden hose up so that it fit into the water passage at the top of the heads where the thermostat housing would go, then I reverse flushed the engine to see what kind of water velocity came out of the lower block. It flowed like gangbusters............WHEW! Cuz I was near convinced that the water passages were blocked due to the age of the engine (untouched since from the factory 1970).
Next, I reassembled the water pump, adapted a hose from the intake of the pump and stuck one end in a tub of water. Cranked the engine and looked at the flow coming out of the top of the heads, where the thermostat attaches. More great news, flows like crazy.
So far so good. I don't think it is the block or the water pump. I used an IR thermometer all over the engine and could not find any hot spots.
Dropped the radiator back in.
New thermostat despite the fact that my old one opened fine in boiling water at 177 degrees F.
Filled it up with water, left the radiator cap off and cranked the engine up. When it got to operating temperature water was bubbling back out of the radiator. Yet another good sign.
Put the radiator cap on and let it run. the temperature got to 190 plus and the fans kicked in.........YES!! (they were not turning on before with a 290 degree water temp measured at the heads).
So the problem all along was a slowly failing thermostat.. Son of a ........
So my completely original 1970 plexi Daytona (blue btw) with 40K miles is still ready to romp and rock.
Thanks everyone!
Ken