The side tanks for the radiator on the ZR1 (same as the run of the mill Corvette) can be replaced without having a radiator shop do it.  Follow the manual to remove the radiator.  If this does not work, here are a couple hints.  The six 7-mm screws down at the bottom where the air scoop is can more easily be removed if the air pump on the driver's side is removed and the horn on the passenger's side is removed.  This gives access for a 1/4" driver + extension to four of the six 7-mm screws from the inside of the compartment where the air pump and the horn normally sit.  The other two screws can be removed with patience.  The radiator shroud may be forced past the stuff on the driver's side and then tilted up to clear the AC lines on the passenger's side.
Pictures tell it all:
Clamping.jpg There is a bed-frame angle iron clamped on both sides of the radiator.  The square stock clamped above  is optional to reduce spreading. The chisel is for leverage to the proper height.
Spreading.jpg Spread the clamp just enough to be able to force the old tanks free.
SpreadClose.jpg This shows it spread just barely off the tank. Note that the side is still spreading but this does not matter. Using a welded fixture would be better.
Opening.jpg This shows it  after the old tank and seal are gone.  Open the tabs just enough to make it easy to put the new tank on but leave the bend of the tabs.
Holding.jpg Center the tank. Grab two ends with a C-Clamp  to hold it. It looks like the tabs can't go over the top to clamp it down but be patient.
Vise.jpg If you are lucky enough to have a 75 lb vise with flat jaws, use it to even up the spread of the sides which will automatically push the prongs over the top of the tanks.  Otherwise use C-clamps to do the job.
Sealing.jpg Use vise grips to seal the top.  Do not crimp too tight.  Vice grips are good as you can adjust the amount of closure.  I set it a little tighter and roll the vise grips up to help get on top with more pressure.
Flang.jpg I set the flange with a hammer to close back the spread and I used vise grips to clamp it down.
 

 by Jim Blanchard
Work Assisted by Wells Blanchard & Tom Dalbeck
Article edited by Kay Blanchard