The current Cascade is not suitable for use with Pelts as I recall. I think he was working on a version that would be though.....
Not sure about WW either...
I do have a Swiftech block though - a couple years old but still does quite well: Swiftech may not be a the forefront right now but they still make good stuff- and having a wb/tec assembly that has been designed to work well together is a good thing.
Heater core: (the search button would answer this as well but here's the rundown.)
Automotive heater cores are what warms up the interior of the car when the heater is on: engine coolant is pumped through it and a blower forces air over it, warming the passenger compartment.
They are designed to be very compact, efficient heat transfer units, which is perfect for our purposes.
There are two main types of radiators common in water cooling- heater core based and coiled tube based; heater core based units are less expensive and perform better than all but the most costly tube types.
And a heater core is less expensive still.
The chevette core is very popular for a few reasons:
common
cheap
perfect fit for a 120mm fan
needs NO mods to work with 1/2" tubing.
Hit google and type in Chevette Heater Core and you should get plenty of pics