225 still running hot

ok so regardless of any degradation. id certainly flush out the radiator heater matrix and block

its set up for the kinda fuel you could purchase 40 years ago. which i guess was unleaded fuel with little or no ethanol..
these days there is a good chance that it has some ethanol in it to raise octane, help with emissions and kinda act like an oxygenator. but it does make the fuel burn slower and in some circumstances hotter. both could make you car run hotter than you would like at idle.

find out its current initial timing. record it
add on 5 degrees to that. see how it runs at idle if it doesn't overheat as quickly, you have found the problem. you need more initial advance, don't drive it like that

set timing back to where it was.

now you would need to choose a method to get more timing in at idle without there being too much at 3000 rpm

easy route, to get you running and driving would be to put the vacuum advance on a carb pipe that always has vacuum one below the throttle blades, rather than one above the plate that has no vacuum at idle. (which is what most 1960-late 80s cars had)
This will cause the vacuum advance to pull in some advance at idle and that advance will fall away quickly as the throttle blades open. it might work very well it may not....

harder method is to recurve the distributor for a more effective advance curve that fits better with modern gasoline i.e more initial and a limit on total

Obviously this is an experiment to see what might be the issue...

Flushing out the cooling system comes first


Dave