New radiator for '86 Coupe GT

[Glenn Kaufman <Glenn_Kaufman.LOTUS@crd.lotus.com>]

Does anyone have any experience getting a new radiator for this car?  Mine is 8 
years old and needs to be replaced.  The dealer wants to charge an outrageous 
sum - about $700-$800 just for the part.  Basically, this tells me he doesn't 
want my business.

I've checked into companies which say they can provide an OE version for 
$225-$275.  How do I know I'm getting a good radiator and are there differences 
which I should look for?  For example, what's the difference in performance of 
it if the tanks are plastic, brass or aluminum?  I know that plastic can't be 
patched.  

Thanks all.  glenn