More than long enough to work out all the air.
If you were to go with a stock type rad you would want to get one like this:
View attachment 1715720109
Your 360 is designed to have inlet on the driver's side top and outlet on the pass side bottom.
Realistically your radiator should be fine. And your fan may or may not be sufficient at idle.
Many above have suggested things to look at before spending any more money.
Timing
Water flow
Condition of the radiator.
Coolant level.
Hoses collapsing, your bottom hose is really long so it could be colapsing.
Water pump cavatsting, or missing fins
Water pump pulley to crank pulley ratio
Thermostat opening all the way and the correct temperature.
Rad cap with the correct pressure ( type 16 lbs)
No leaks in the system ( holds 16 lbs)
First you need to determine what temperature your engine is running at with a real temp guages of some kind.
What ever you do, do not put a shroud that is flat and close to the rad. It will block air flow at speed, you might be good at idle but then give problems at speed.
