I got the Griffin 31x19 Ford Nascar style universal radiator from Summit. Just had to drill holes in the lip for fan shroud and get a different lower radiator hose.
If it is the FMS-8005-C it is really a 2 core that is about 2.25" thick. It cools my NA 306 pretty good except it starts to get temp creep at 100*F with the AC on. This is with a Mark VIII fan. The good news is the temp only increases about 0.9*F/*F ambient so it doesn't want to run away. If you have to run in high ambient then make sure you block all open areas on top and all around the radiator.
I have a 2 core replacement in my 82, from radiatorexpress.com, for about $105. The 3 core was $10 more, and I was too cheap and did not want the extra weight, so I got the stock replacement. Has worked fine for 4 years.
Carquest, Autozone, etc, all have inexpensive drop in replacement radiators.
I used a Ford Motorsport M8005 in my 79, about 10 years ago. It probably drops in an 82 or up, but hit the 79 ac lines, and had to be moved off to the left about 3/8 inch. But it has worked fine for 10 years or so.