svshaaw82, Sorry about givin ya some bogus numbers for the 242 (4.0).
Looking back now I've only done 1 stock 4.0 engine and between having
a long day and having incorrect information from two different sources I didn't catch
it.
Going back to some of your questions.
The recess in the piston dish, or cup has a volume that has to be measured and calculated the same way as you would the cylinder head combustion chambers, including the volume of the head gasket.
Your correct that your .116 dish is going to be about 15cc and compressed .043
gasket with 4.00 diameter will give you another 8.85cc
ICON as you referenced, is making a piston formally made under their parent company Kieth Black. To my knowledge they make only two variations of it's forged piston for the inline 6 cylinder Jeep engines.
The IC944 has a cup volume of 21cc. The other piston carries a part number IC945 and
has a smaller volume of 10.8cc.
Both of these pistons are meant to be used for 4.6 to 4.7 stroker combinations using a 258 crankshaft with a stroke of 3.895. With a C/H of 1.353 you can use the longer 6.125 4.0 connection rod that came in all 242 engines.
The way I see it is you have three cost choices with pistons for your 4.0
Silvolite makes a piston with a part# 2229. It's a cast piston with a .100 recess D-Cup with a volume of about 11.5 cc. with a C/D of 1.581
Seal Power has 2 piston options.
677AP is a cast piston with a .116 deep recess measuring 15cc and a C/D of 1.585
H825CP is a cast hypereutectic piston that has a teflon coated skirt.
It also has a .116 recess, but has a 1.592 C/D
The other obvious choice is you can machine the C-cup lower in any of these pistons to get more volume. For example. I'll trace the pocket to a total depth of .200 and increase the total volume to 26cc.
There are several ways and methods to come up with a desired compression ratio to run on a specific octane fuel. It is my opinion that in a normally aspirated gasoline or alcohol fueled engine you want the piston ATDC to come as close to hitting the cylinder head as possible without doing so. All things being equal, this will give you the best combustion/burn possible.
Hope this helps and gives you something to think about.