My radiator is a 2 core. Griffin 6-567AR-BAX
"Griffin rates this rad with a proper fan and/or shroud capable of cooling 400 to 600 horse power engines. It has 2 rows of 1.25" tube size."
So that discounts the 3/4 core incompatibility.
If the lower aftermarket rad support brackets are stock for 2 core, it should fit.
I think we'll end up removing, cutting, separating and re-welding the lower rad brackets to match the top, and get new pads for both top and bottom, all the same length (as the old top pads). None of the pads I got from Early Classic will work. More wasted money.