You shouldn't need to helicoil the head bolts unless they're damaged. I'm in the middle of rebuilding a 560 myself (although mine is the SEL) and I did wind up helicoiling some threads, (one head bolt and 2 of the little guys around the timing chain). Only helicoil them if the threads are damaged or stripped. Before putting the head back on, take a bolt and test it in each threaded hole, if it goes in cleanly, call it good.


Best of luck!

Scott