If the head is completely rounded beyond hope, you will have your best chance of success by using a bolt extractor. A common brand name is "Easy Out".
There is a pretty good how-to at the link below. One thing I recommend is when you drill the hole, use a moderately dull bit to enlarge the pilot hole. That will cause the bolt to heat up and take in the penetrating oil that you have squirted on the threads.
One effective way to remove a stripped allen bolt is to use a screw extractor tool. This tool can grip onto the bolt and help twist it out. Another method is to use a drill to create a small hole in the bolt and then use a screwdriver to remove it. It is important to use caution and proper tools to avoid damaging the surrounding area.
One effective way to remove a stripped hex bolt is to use a screw extractor tool. This tool is designed to grip onto the stripped bolt and turn it counterclockwise to loosen and remove it. It is important to use the correct size extractor and follow the instructions carefully to avoid causing further damage to the bolt or the surrounding material.
Remove the third bolt !!
Spray it with a penetrating oil leave it for a few hours then try to loosen it, or heat the nut up quickly and try to remove it then.
Remove the lower bolt from under the truck. Remove the upper bolt by removing the left front wheel and getting to it though the wheel opening. Not easy, I just changed the one on my 2.7 Tacoma last year.
Use a bolt extractor to remove the broken battery bolt..This is the easiest way...
Torque Setting for VS Commodore Harmonic Balancer Bolt- between 270-320 NM. The Best way is to check the bolt torque setting before you remove it.
counterclockwise
Unlock and pull the bolt as far back as possible. Once it is all the way back, pull the trigger and pull the bolt out.
You don't need to remove the bolt. The mounting bracket is slotted so that you only need to withdraw the bolt a small way and then pull the alternator and the bolt will come out through the slot.
Simple as Pie. (or PI). Remove the buttplate screws and buttplate. Unscrew the buttstock Bolt, all the way, with a LONG screwdriver, remove the bolt and slide off the stock.
Most motorcycle ignitions have whats called a "shear bolt" I think, they're designed to "shear" off the hex portion of the bolt when installing the ignition. This prevents theft. Usually to remove the cone type bolt the best way it to use a steal center punch and hit the head of the bolt to turn it counter-clockwise to loosen it. If it is too tight to loosen this way unfortunately the only other option I know of it to drill the bolt out. Good Luck. MotoMedix Ottawa.