13:1 Compression Stock Stroke 400??

The “standard” BBM Ross dome is 14cc.
If you had some pistons made to fit your rod/stroke with that dome, zero deck, 75cc heads, and a .040 gasket you’ll be at about 12.5:1

Frankly, just going for more stroke and using an off the shelf piston makes a lot of sense(unless there is a pretty specific reason you want to use the stock stroke), and wouldn’t add much to the build cost really.

The same dome volume piston used in a 451 with an 80cc head will get you to 13:1.

Chrysler Big Block: Open/Close Chamber: 400 - Dome Top: 4.375 Bore - 3.750 Stroke - 14.00CC - #99499 - Ross Racing Pistons