Not sure if this is what you are asking, but If I was trying to graft the bottom rail of one rad support onto another and make it look "factory", I would drill out all the spot welds, get the bottom rail off, weld in all the holes on both pieces, grind the welds smooth, then punch new holes where your want the plug welds to be, and weld the rail to the rad support.
There is a special pair of pliers with a copper pad that you clamp under the spot weld hole that makes it easier to weld in the holes you drilled.
https://www.amazon.ca/Steck-Manufact.../dp/B000RFMAGK
Also, when I say "grind down the welds" I do not mean with a grinder, I mean with a 36 grit 2" roloc sanding disc in a right angle air die grinder. This works much faster than a grinder, is easier to use, and creates less heat when grinding.
__________________
Michael
Oshawa built 1 option Judge basket case. 463, SD KRE 295's, CNC'd factory intake, Cliff's Qjet, Stump Puller HR cam, RARE RA manifolds, Pypes exhaust, T56 Magnum, McLeod RXT clutch, 3.42 12 bolt.
24 year project almost done...
