390 overheating issues

[OzStang390]

Definitely 148mm diameter.
2 grooves.

You could see if Bill Upham has any at Mansfield Mustang or West Coast Classic Cougar.
http://mansfieldmustang.com/

Thank you for measuring your pulley for me, I finally got a chance to measure mine today and it's the 148mm diameter pulley, so I guess that's not the problem. It look like the engine has to come out and be stripped unless I try an aluminium radiator, I have heard opinions for both sides of the coin on these aluminium radiators, the who swear by them and those that swear at them... I'm not sure who to believe and I have already spent way more than I ever intended on this car but I either need to get it running or part it out... which is something you don't normally hear on a full rotisserie rebuild, BUT... this car has eaten into the inheritance money left to me to fix up our house and I cannot justify spending much more money on it. Have you ever measured what temperature your car runs at?

Mine seems to run nicely at about 84°C while driving at constant speed, especially at 100 KMH, its when it's sitting at traffic lights or just sitting stationary (like after a drive, idling away), but once the heat builds up, then it sits at the higher temperature and doesn't return to the 84°C.
At 84°C the temperature gauge on the dash (Dakota Digital) sits at the halfway mark in the "normal range", but if you sit stationary in traffic or hit an up-hill slog, then it climbs to the high end of the normal range or higher, I have had it hit the letter "H" which I believe was around 125°C which is very disconcerting as you watch it climb to that point.

[hybrid]

If you go aluminium, don't fall for the 4-row, 5-row BS.
With aluminium, what you want is big cores. So at least 1" cores.
More often than not, the 4 row and higher (and sometimes even 3 row) are 3/8" cores. Don't use those.

You are better off with 2-row 1" cores than a 4 row 3/8" cores.
The benefit of aluminium is that it's stronger and can handle bigger core length than copper/brass, so much more surface area for the fins.

[Keegan]

Without seeing your car, is the flow of air to the front of the radiator impeded in any way? Like aftermarket grill, lights, aircon condenser, oil cooler, even an oversized licence plate…that could be blocking fresh air from coming in.
Also, have you installed a quality coolant?