azblazerboy,
I had not heard of Eckler's either but here is the website
http://www.ecklerstrucks.com/. I ordered one from Ecklers’s Trucks because I called Advance, Oreilly, AutoZone and NAPA locally and they all had the aluminum heater core. The Eckler's one was more expensive but if it is copper/brass then I think it will be worth it. I'll post pics when it comes in and let you know how it fits.
Nate