Hang the car as high as possible then hang the piston with another jack clamp.Make sure you mark the jack so you will know your difference from as high as you can hang the car vs your six to seven inches of runby till you should hit the stop ring. Now you can remove the head. Measure down to the stop ring. Do your math twice to be sure you have the right distances figured out. Put everything back together and land car on pipe stands and lower piston and remove the head like you were going to repack. Have a piece of pipe cut that is just big enough to slide over the piston on the inside and just big enough to fit inside the bottom flange of your head and of course long enough to match you distance yo need to reach from your old stop ring to where you want it to hit now. This could be a couple inched to 12 foot if there was a future floor. Make sure you jack stands are long enough to math or you may need a couple sections of pipe if you have a jack with several future floors. We have done this in the past. Just slide the pipe over the piston. Ours was snug enough it didn't just drop down. So when we put the head of the jack back on we just ran the car up till the pipe bottomed on the stop ring and we were done.