First off, GREAT looking motor there My First!!
Please look into a Summit's House brand, Northern Aluminum radiator for your car.
See the two flanges on his rad. top. I just took and put four about "flange height", (3/4" I think?), aluminum square tubes across them on each side, top and bottom, then put a 1/8" x 2" thick aluminum strip on top of them and pop riveted them all together and the drilled four 3/8" holes in the rad support two, top and two bottom and then used washers and rubber to space it out so it is about 1/4" away from any possible rub point!!
Sucker looks like it belongs in there stock, or at least to me!!!
I did it this way b/c I only paid like $160 or so for the rad. w/o side mounts but if I woulda got the correct side mount one, it woulda been alot more expensive.... I ran my '66 Buick, four core stock rad. the same way at the tyop for several years with a strip of "Plumbers Helper" across thwe lower part tp clamp it along with several thick pieces of rubber. Worked fine but it didn't look very good down low, but the top was fine.
If I had it to do over again, I would center my bolt holes to the rad. support opening instead of the rad. b/c it is offset so my bolts aren't symetrical and centered sorta deal is all.....
I'm just "nit-picking" myself is all.....