I have used several welded aluminum radiators on TF trucks and they worked well. Not sure about painting the aluminum though and how it would affect the cooling. I have not painted any of them. Radiator shops use a special paint on brass/copper radiators.
Fred

1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine