I decided to install a 24" radiator in my 66 convertible project.  After some research I ended up with a DeWitt's 379 style radiator - big block 67 to 69 and/or 70 small block with A/C which has a passenger-side upper/inlet and driver- side lower/outlet.  Very pleased with the radiator construction and the price was about $100 less than an equivalent Griffin.  It is a two-row aluminum unit and the upper tank is dimensionally similar to the original four-row radiators.  I started the installation with the upper bracket and quickly figured out that hood clearance might be an issue.  After a few emails with MustangSteve I learned two things - a paint stick is required for fitment and it ain't rocket science (in other words I was over-thinking it).

First - the paint stick - place a paint stick across the frame/body area in front and drop the radiator in place.



The lower brackets extend across the strut rod support brackets and the radiator support in this area.



After checking the fit and spacing, my radiator fit a little better with two paint sticks and the position of the radiator filler neck and cap would still clear the hood.  I made basic brackets cutting some scrap 1-1/2 square tubing and used a portion of the lower radiator support brackets I purchased - save your money and make your own.  The brackets are about 3-1/2" long and are 1/2" thick/deep at the back end and 3/8" at the front end to account for the radiator support sheet metal.  Here are two views of the simple brackets.  





The filler on the raditor is not centered.  However, when installed the filler neck is centered in the car.  This offsets the radiator towards the left/driver's-side of the car by about 1" and provides more room for the battery.  To fit the lower support area of the radiator the brackets were also offset towards the left.  The next pictures show the radiator tank with the offset filler (this is offset is the same as the original radiators) and the lower radiator support area of the DeWitt's.  The DeWitt's differs from some of the other radiators in that the lower mount area is not part of the lower tank but instead they are fabricated from square tubing.





This view shows the driver's-side bracket in position on the frame.



The brackets were tacked into position, the rubber pads were inserted and the radiator was dropped into position.  After my initial mistake of installing the upper bracket at the top of the radiator support I was left with the alternative of filling the holes or slotting them.  For now, flat washers hide the slots and I doubt anyone will pull the bolts at a car show to see if there are slots.  I added a flange to the hood latch mounting frame but if the radiator bracket holes are low enough, this is not required.



If I was starting all over knowing what I know now, I would have dropped the radiator onto the lower brackets and measure where the upper bracket sits below the top of the radiator support.  Pull the radiator and place the bracket back in position and mark and drill the holes through the radiator support and the hood latch.  This picture shows where the bracket sits in my installation.  All cars vary and the radiators may vary from one supplier to the next so mock up and measure for a custom fit.



The next pictures show the final fit on top and sides.  The radiator support opening was modified according to MustangSteve's big radiator installation instructions which opens the area to match the radiator.  I have some rubber trim that I will install around the sharp edges after paint.  The overflow hose is going to be a little tight so I may notch the top of the radiator support slightly to clear.  After fitting a big block fan shroud, the next step is to fab up the revised battery tray.  I tried to install a late model reverse rotation clutch and fan from a '91 but there is not enough room so I am installing an 18" reverse rotation flex fan.  With the radiator in position I have about 1" clearance which should be close to ideal with the shroud.  Thanks for the support Steve!