My 65 is the hottest around the block

[induction]

I see your in Ontario!! I use to live in Pomona!! Try Victors Radiators in Pomona on Holt ave. They are located just behind Weinersnitzel next to Aamco, just up the street form Saint Joephs church which is across from Gongoras paint and body shop ( the best paint shop from San Berdo to LA! IMO
Anyway..

My '65 had an overheating problem at one point but it was solved by having the STOCK radiator roded out. I then flushed out the block, replaced all three hoses and added a ' inline filter to the upper hose and after properly removing the air from the system she never ran hot agian. (Remember on a stock radiator you must leave some air space fron the top of the tank. Don't over fill) I did the first cleanout of the filter about once a week for the first month and you wouldn't believe how much junk was trappes in it . . Here is a link to where they can be ordered. they can be found locally as well. Ask a good radiator repair shop if they carry them.
Note.. the 289 blocks are known to rust ect internally over the years.

Hope this helps, Let us know

Once installed in the upper radiator hose, this full-flow reusable filter captures debris before it can clog the radiator and heater core. Available in high temperature clear plastic (for easy viewing) or NEW heavy duty, machined brass style. Aircraft style hose clamps and instructions included. A must for any liquid cooled vehicle!