Looks like an ordinary pop rivet tool, but in fact is for fitting threaded steel rivets. After some measurements and drilling the necessary holes, the rivets could be fitted;
The end result will enable me to fit the mud flaps without much problems;
Only job which needs to be done is welding the back of the rivets to the body, just in case they decide to lose some of their clamping force. I also need to drill a new hole in the left hand rear wing to fit a nice period aerial. And one of the welds from the RH front towing point is cracked so needs to be repaired before next week.