For the top I made these brackets and simply pop riveted them so if I need to replace the rad I just drill out the rivets and transfer over the brackets to the new rad. I also mounted the top in these rubber well nuts
( available at Lowes) Holes are already there. I might have drilled one more can't remember it was 5 years ago now. I used stainless steel carriage bolts then milled the flats on them so I could hold it with a wrench so it wouldn't spin when I tightened it. Used washers to space it away from the core support and locknuts.
I'm into the K.I.S.S. method.... Keep It Simple Stupid.... and cheap!