Replacing my crushed and rusty tank, and had both bolt heads shear off as i was removing the straps. I couldn't get them to move with vise grips and as much pb blaster as i could put on them. Drilled out the passenger side one, as i can just put a nut on the back end. The one nearest the tow hook is another story.. It won't budge with vise grips, and there is nowhere to put a nut on the backside if drilled.. I have a tap set is that my best bet?