Thank you for all the responses. Let me explain why I'm asking for a source to buy cores:

1- As mentioned, there are very few radiator shops around any more. I called one local shop and was quoted $850 for a re-core.

2- I called another local shop, and they were interested in working on large commercial units.

3- I called Glen Ray over a year ago and left them a voice mail. i asked if I could send in my tanks and brackets for a re-core. I never got a call back. No I'm not interested in paying $1000.

4- I talked to classic industries regarding the published information on small block radiators. I sent pictures showing that the nipple points to the passenger side on 73 and 74 cars. That is where the overflow tank is located.
The person i talked to sent an email to Mark Worman asking for his input and copied me. Mark Worman never responded.

5- Yes I can buy a radiator from classic industries and go through the effort of having the filler neck indexed correctly. That is a radiator that does not show correct part numbers, and has an additional hole that needs to be plugged.

Having said all that, it makes sense to me to try and purchase a core if possible and swap out the tanks. I've rodded out a few radiators over the years. It's not that difficult.

What I did not mention is that I have another radiator that also needs to be re-cored. It's for the 1970 Challenger SE big block I'm restoring. I'd like to keep the original tanks.

It appears from what I'm seeing that buying cores is not going to be option. Next thing I'll have to try is widening my search radius and going an hour or more out of this metro area.

Thanx again for everyone's input and help.

If anyone form Minnesota can recommend a radiator shop that they've dealt with I'd really appreciate it.