It is essential to keep the fins straight and clean. Painting will reduce the cooling efficiency and make repairs difficult. Use only Aeroquip, or AN840 fittings. They cost more but are worth the money. It is your life that depends on their quality.
Caterpillar dealers have also some lightweight, plotted, quality steel fittings.
Check them out. A cloud of steam from your engine compartment shortly after takeoff can give you both.