I am going to be watching to see what info you get on the plugging subject, as I posted a similar question earlier, lotsa views, no replies. I believe 1-2 internal plugs or "redirect" valves need to be removed or reinstalled to do this, but I have not been able to find out exactly what I need to do. Don't want to do the wrong thing or plug the wrong port and frag the motor. May just suffer and run the cooler, motor is planned for a 71 Vette.

On cleaning your existing cooler and lines, should be able to use some kind of solvent or parts cleaner and run it thru and flush it out. Maybe a radiator shop, or even and AC shop could help. The AC guys have to clean condensors and evaps all the time when a compressor destroys itself.

Finally, out here in SoCal, the you-pull-its have lots of later GM trucks and vans with big blocks and/or oil coolers. Maybe you could find a clean on in a yard?

Good luck,
Tom