I am not sure of which flat top pistons you have, but here is some info about a good KB piston I found at
www.hughesengines.comPart No. Part Description
2005 318 Flat Top 8.9:1 With 70cc Heads/ Keith Black Hypereutectic
For 318 V8 and 3.9L V6 engines.
Compression ratio with head CC size.
58cc = 10.2:1
62cc = 9.7:1
70cc = 8.9:1
74cc = 8.5:1
636 grams w/ pin
Effective dome volume -5cc
Compression height 1.810"
Deck clearance .011"
All compression ratios are based on a .030" oversize and a .039" compressed gasket thickness. Piston deck clearance is based on a block, crank and rods with factory perfect measurements (which, due to poor factory quality control, never happens). All Keith Black pistons have generous valve reliefs to clear most high-lift camshafts. However, always check piston-to-valve clearance prior to final assembly. All Keith Black pistons can be used with either press-fit or full floating wrist pins. All pistons use 5/64", 5/64", 3/16" rings, except for Diamond Racing pistons which use 1/16", 1/16", 3/16" rings, unless ordered otherwise.