The plastic end tanks are far from perfect, but they are better quality than the brass ones they churn out these days. We had to have the top tank replaced on one of the work Falcon utes with only 50,000km, but my one has done twice that with no problem.
In the meantime, we have replaced the heavy duty Landcuiser "traditional" radiator 3 times (1xoriginal, 1xnew after market, 1xrecond exchange).

Ideally I would have aluminium end tanks - if the plastic fails, I'll knock some up and weld 'em on.

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Too many cars, and too little time.

I hate plastic tanks on alloy rads-

1. Ford Probe, son's car- (Mazda rad) rad was fine, gasket leaking under plastic tank... nope, no repair kit available.. New rad is only $750 or so.

2. Ford Laser `92 (Mazda rad)- top tank cracked where the idiots designed a groove for the overflow hose to clip in it. It just fatigued.
Had to get a changeover rad, but the core was fine- Natra said "Oh this is a common problem".
Bastard designers..

3. Ford EA, repeated overheating only when I had the boat in tow.
Bloody 2 core alloy rad was clogged "Oh yes this is a common problem". crap I've heard that phrase before..
So I put a REAL brass 3 core (taxi) one in. No more problems.

Soooo, youse can all keep your &^$%$&* alloy rads..

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.