Cold Case is here to help
Hi Chris :D
As a very long-term member and fellow Vendor on Joey's forums, I suggest starting a new thread but post it outside of your own forum. Put it in the General Discussion, Tech and Racer's section. Announce your R&D needs for every model you're planning on adding to your inventory eventually.
Those very same people you're trying to serve will go out of their way to help you with measurements, pictures, and even take the time to draw diagrams for you ... because you'll ultimately be helping them as well as our entire hobby / industry.
Over a hundred thousand devoted members worldwide, all eager for what you're offering, will also be the first to tell you what they need and want. You just have to ask them somewhere that they'll see it, and then take note of the responses.
If you're clear in your announcement, everyone reading it will know they won't be getting welded up tomorrow. But together we can all ensure the ones we need for our old cars may be there some tomorrow.
FABO members have chosen my shop's posters, t-shirt design, and the shape of my "Hand Job" Soap Customer Appreciation Gift. One wonderful guy madmikee even devoted his personal time to surprise me with the logo I still use today.
They're your best resource, and almost a captive audience. Tap into it.
And when someone's valuable input launches your new line of 1965 A Body rads, tag the person who helped. It's not only a great reason to bump your R&D thread for more views/input (with a link to the new radiator post) but builds goodwill and friendships to last a lifetime. You might even be able to work it into your banner ad, though they're often ignored.
Just a suggestion from the cheap seats. Best of luck for every success!