Here some pix of the new heater core that arrived this morning.
It is a heavy sort and coated with tin all over. The hoses are to be fastened with the supplied clamps, sealed with one O-ring each. It also comes with some self-adhesive foam strip, presumably for sealing the closed regulator flap. The name of the brand and part number are clearly visible below.
The manufacturers home page:
Alternative source that ships to the States:
Maybe I'll post a HOWTO when I get to putting it in, and have a look at the muck clogging the original part.