I have a heater core from a '87 chevette and it was a full copper unit that looks exactly like the D-Tek or Big Momma units (once you solder on barbs). I'm pretty sure all the later models came this way as I removed a half dozen to find the best looking one, and they where all the same and all copper.
Secondly you can't go cheap watercooled, if your just starting to overclock and your broke get a WBK38 heat sink or something cheap (theres probably better low priced units now). You should be able to overclock quite well if you select a good heat sink. I ran my 1.33g at up to 1600 and it was just at the 50 area full load (around 25 in room), fully stable. Check the other forums.
Otherwise Resago has a mint combo (mine
), I'd just be wary of Home Depot hose and get something like silicon that's more flexible (as stiff hose rocked my waterblock off, and I burn't a 1.33 before it got to Windows to check temps)