340 High Compression Pistons

Hold the phone OP.... you are so close. I'd like to ask why the high CR in the first place? If you are running a fairly radical to radical cam, then it is the right thing to have to keep dynamic CR up.

The closed chambers mean that you need to be ready to machine a domed top or have the right shape. But the Indy X chambers are not severely closed chambered, and IMHO the machining will not be severe to get the 99626's to fit. There is just a small cut to clear that angled edge of the chamber over near the spark plug, and a spark slot to add. And their compression height fits right with your decking the quench side of the chamber works with the flat on the Ross piston.....

IMHO, check with Ross to verify the pix on the Summit page, and dimensions on the quench flat area. If it looks good, see if you can buy ONE from Summit and look at the fit versus the head chamber, and take it to the local machinist. Look under the dome to see if their is meat to support a machined top. A lot of this can be done with a call to Ross.

http://www.summitracing.com/parts/ros-99626

#8---La-X and Ma-X Iron Small Block Heads