Need to Re-locate Factory Parking Brake Cable Guide/Bracket

I am in the process of changing over the '65 Formula S parking brake set-up to the later style with the main cable not crossing over to the passenger side. I need to remove and re-attach one of the guides but I am not exactly sure how to remove it without destroying it in the process.

If I drill inside of each of the two "indentions" will it fall off? I'm not a welder, so just by looking at it I can't tell what holds it on to the underbody. I think the spongy looking stuff in probably leftover undercoating. Thank you.

cable guide 1.JPG

cable guide 2.JPG