I'd highly recommend the 4.25 stroke. That combination basically falls together and then you plenty of clearance for the windage tray and the internal oil pickup. Just buy a high quality 4.25 stroke crank with 2.200 rod journals and get a set of good 7.100 long BB Chevy rods and you're good to go. Most anyone should be able to make pistons for that combo, might even be a shelf piston at JE or Diamond.

So if I put together a 540 with mopar heads,10.5 compression and a cross ram/ with a hydraulic cam what approximate horsepower can I expect? Would like to have car run high 10's if possible.

Hemi piston 4.5 stoke 7.045 rod

440 piston stock stroke 6.76 rod. Plenty of room to go up on this piston

Hemi piston, stock stroke 6.86 rod. Add 3/8 to stroke and 1/4 rod length, can't see now way to stay out of oil ring, am I missing something here.

These are 572 Diamond Pistons that I got from Ray Barton for 7.10" rods.

Piston info

Ray prefers the 528. We put a flat tappet 572 in a 3550 lb 70 Cuda (former Super Stocker so it knew how to hook up and go) and went high 9's. That was a drag car with slicks and 5000 converter. Modern flat tappet, single 4 bbl, 528/540/572 engines, done well, make over 800 hp.

Sorry, I'm not following what you are saying. Put what 2 side by side? But, compression height on a hemi piston is not to the top of the piston.

Nevermind Rick, I figured it out. The "perspective" wasn't turned on the stupid software. Operator error! They would have looked identical except for the dome not modeled on top. deleted the post.

I will add, my piston was for a standard deck height with 7.1 rod. My deck being down .130 I found a 7.045 rod, still a little tall but I'll take it up with a thicker head gasket.

Modern pistons have.990" pins and much smaller ring stacks. That helps this all fit together.

Thank you all for your input. I will start gathering parts for the build. Most likely will go with the 540. I will check with Barton and Tim for rotating assemblies before doing anything. Appreciate your replies.