My recommendation is to find yourself a good 'ol radiator shop and have your Harrison rebuild. They are good radiators and a reputable old time radiator shop can clean and re-core your old one. Ask them to put in a high efficiency core, especially if it's a 4 core and you have A/C. I had mine done and am running a HD fan clutch and run 180F all day long......
I had it tested at an old timer's rad shop, or so he said. It's not leaking and he said it would be too expensive to recore ( 4 row original man trans) but it was still in decent shape.. If I felt like I trusted the dude, I might go that way. I know my Lemans runs cool with the aluminum , two 1.25 tube rad and much more efficient than copper/brass . As far as having a rock hole fixed when I'm out of town, SOL I guess.