Aluminum Radiator

As to the clutch;
Running direct is better than clutched, obviously; because the directly driven engine fan does not slip on the water-pump axle.
There are advantages to running a clutch, but you gotta get your system sorted out and dependable first.
Make sure the fanbelt is not slipping.
FWIW
I run a stock ancient 1973 318, A/C rad in the stock core-support,of my 68 Barracuda, in front of my 367HO combo; and it has no problems keeping my engine cool.After I proved it with a direct-drive fan, I subbed in a viscous coupled 5-blade fan, which failed. Then a T-clutch off a 2000 or so Ford pick-up. But the 5-blader was not enough. So on went to the 7 blader with the T-clutch. At this time I had had enough, so I also installed a Milodon Hi-flo waterpump. Between these two my problems went away, so I started to run more heat into the cooling system; first a 180 stat, then a 195, then a Milodon hi-flow 195 which actually operates at ~205*F at the stat-house.
I suppose I could go back and try the 5-blade fan, but this 7-blade system runs rock solid at ~207, so I ain't messing with success.
Additionally the system has always had a shroud, an expansion tank, and when I was having problems she ran straight water. After I got it sorted, it now runs 50/50 plain old Prestone antifreeze..... so I don't have to drain the water out every fall,anymore.
Oh yeah, after I got it sorted, I played with pulley sizes and got the pump slowed down. This so I could rev to 7000 and not have to worry about the belt flying off. That belt was new in 2002 or so. The brand new spare is still in the trunk.
Ok now
I highly recommend a compression test. And to make an ignition timing map.
Say what?!
Com'on it's a 1973; they ran fine when new with your exact system.


BTW; nice car