How do I compress radiator spring to get nut on?
I blocked the stud with a piece of wood and had plenty of room for the parts to start the nut without worries
Sometimes it takes the block of wood and a socket stuffed (paper towel will do) to hold the nut so it doesn't recede into the socket and long extension to press down and turn. With new hardware that was what I had to do to get the nuts on my 26 radiator hardware.
I got a small pair of those c-clanp vise grips and clamped the radiator shell/radiator to the top of the frame rail from inside the hood. That will compress the top spring then I could get the nut started.
I got it! Used a c-clamp just the right strength and went from bottom of axel to grill shell with a piece of leather under it.
On the 26 I put on first the oblong nut with spring under chassis and install a cotter pin. Then I put on the spring and lower thimble on top with the nut. I tighten all the way so the stud has no threads on either end or the springs are completely compressed. Then I block under the flat nut at the bottom. You can use a small block of wood or anything which fills that space. Next loosen the nut on top to the point you can get a cotter pin through the castle nut continue to loosen which will unscrew the stud from the lower oblong nut until you reach the cotter pin underneath. Then remove the top cotter pin and remove the nut. This should leave enough of the stud exposed on top to where you can install the radiator. After you get the radiator on and the top thimble and nut on, you can remove the block under the bottom nut and adjust to get the radiator straight. I know as I described it, it seems to be quite a job, but it only takes a few minutes in actual practice.
And of course, don't overlook the fact that some of the springs are coming thru from some vendors WAY TOO BIG and that might be your problem. Also, the "pre-26" kit has shorter studs and it is possible it was packaged wrong or pulled wrong from the vendor...