to make the tabs jg
Same lights as I used
shown in this pic
is the fact that the wires which power these lights run through & out the bottom of their mounting stalks,which means that even if the threads on both were the same you'd have to end up drilling all the way through the add-on brackets
& into the frame tubes & run the wiring to them from within the frame tubes which,in part,was what you were trying to avoid in the 1st place along with welding tabs & repainting.
What I used were just 2-1/2" ID radius EMT clamps
bolted to the frame & an external harness to each light ziptied to the frame
also presents another problem in that you're running a removable engine cage on a semi-full bodied car = those lights(& their wires) are gonna be dedicated to that cage seperate from the rest of the body of the car,so you're gonna need to make some quick-disconnects between the car & the cage in order to be able to service(remove) the engine & trans if neccessary:
I guess we have to have a way of disconnecting the the wiring to the bumper. I need two connectors with two five contacts each.
from page 10