340 with edelbrock heads overheating

Early a body said
340 .40 over with less than 1,000 miles on rebuild
stock pistons
flat tappet cam
initial timing at 12 degrees
edelbrock avs 800 cfm carb
1964 dodge dart

I decided that i would swap out the x heads to eddelbrock 340 heads.
Installation went fine but now i have developed an overheating problem.
At idle it will heat above 210. I have not tried to see where it would stop i just shut it down.

the radiator i had on it cooled just fine would not get past 180. This was a champion 2 row 19"- this is on a 64 dart

Changed to a wider 22inch 3 row champion radiator that i had stored away. no difference
changed to a 160 thermostat . no difference

Using 273 adjustable rockers and double checked to make sure the valves are adjusted properly

coolant looks good . I am using prestone 50/50 premixed

oil looks good Valvoline 10-30 vr same oil i use in all my flat tappet cars

Not sure what else it could be. Did the head gasket blow but did not cause cross contamination of the oil and the coolant?

Thanks in advance.

First, a fresh engine will tend to run warm until "broken in". This is not as much a problem with the newer rings and cylinder hone finish they require. 50 to 60 years ago the chrome face rings reqired fairly course hone stones to allow the rings to wear into the cylinder walls. This created a lot of friction. One guy I worked with rebuilt a 390 and it was so tight the starter could not turn it over. They towed it around the block to get it started. Ran hot for a couple of weeks and then warm most of the summer. Once he got about 10k miles on it the temps settled down.
Considering you will have modern cylinder finish, I would not expect this to be a concern.
With the recent assembly with new heads, is it possible the head gaskets were installed front to back or upside down,blocking coolant passages or closing the rear and leaving the front open allowing the rear cylinders to not receive coolant flow?
Was a new thermostat installed that may not be functioning correctly?