You can find a very original looking aluminum radiator on eBay for a little over $200 last time I bought one pre COVID.
I primed the top tank, bottom tank and the sides with Rustoleum self etching primer then Rustoleum gloss black. Looks great 10 years later.
I did not paint the fin area. No need to because its hard to see anyway.
I bought the standard size radiator and they do a great job of keeping a 350 in a '49 3100 cool with a flex fan.
