Do you have a radiator picked out? Do you plan to install the rubber filler pieces along the edges of those radiator side panels?
My '66 didn't have a radiator when I got it, but the brackets for the upper & side seals were still there. Since I put a 454 in my truck, I had planned on buying a premium US made radiator that came recommended on another Chevy truck site. But I stumbled on a Amazon 4 tube unit for the '66 for $200 delivered. I figured I'd use the cheap rad to get the truck running & finishing the build. Then purchase the USA unit when the truck is ready for the road. But the El Cheapo looks & fits so well, including the top & side baffles & seals, that I'm going to use it till it fails, for whatever reason. I did have to flip one of the baffles over in order to pick up a little more room for the side seals to fit, I also glued the side seals rather than use staples. Pics are on my phone, so I'll have do a follow up post with them.
1966 C-10 Short Stepside HiPo Step-by-step ~ and on-going resto build in the Project Journals