What is the core clogged with is the real question. If you want to reverse flush it I would remove the hoses where they go into the firewall and flush it right there. If you do it this way you might want to pick up an O ring kit before you do, the metal tubes are sealed with rubber O rings and yellow plastic rings stacked onto the metal end and are real easy to loose. I think the kit is about ten bucks or so. If your car is a turbo you might find it a bit of a bitch to get the hoses out and a garden hose in there and may want to opt for just pulling the core out, it is not that big of a deal and if your core is clogged internally you may find yourself doing it sooner than you think anyhow. How about the rest of the engine, is it full of rust and crap too and if so why?

Mark