He didn't just go one size over but two to make it a little harder for me to correct the situation. Stock size is 8 X 1.25 and the current bolts are 10 X 1.5.
Well what I settled on is just about the best thing a guy could do in this situation.
Problem=Money
Apply Money=Problem solved
I bought a Time Sert Big Sert Kit. Bst thing I ever did. The procedure was simple and with the supplied pro grade tools made a hack like me look pretty good.
Yes I know my engine is GROSS!! Due also to the port spooging all over the place because the old head pipe was loose because the bolt hole was sloppy and then the bolt could not be tightened properly.
Here is the kit with a stock bolt and the offending oversizer

Here is the hole drilled out and then chamfered.

Threaded with the supplied tap.

Insert ready for installation.

And then The final result.

I also have a few inserts left over in case this happens again.
Helicoils are OK in my book for some repairs. In this case though it was best to spend a little more and get it done the best way I know of.
edited to add: I meant to put this in repair