Using the Eagle calculator I come up with a 11.77 to 1 compression ratio (more that 11.5 to 1 because of the .030 overbore) using 9.599" deck height, 4.07" cylinder bore, 10.7 cc dome volume, 72 cc combustion chamber volume, .039" head gasket, 3.31" crankshaft stroke, 6.123" connecting rod length, and 1.84 piston compression height. It also shows that with above specs the flat part of the piston to be above deck by .019". (it reads -0.019" on Eagle software)
P.S. With a 68 cc combustion chamber/cylinder head volume Eagle shows a 12.47 to 1 compression ratio.
I am using these same pistons (TRW L2322F + .030") in my Mopar 305 CID built motor using a 2.96" stroke, a 6.298" connecting rod and 72 cc CC volume open chamber heads where the Eagle calculator shows only a 10.63 to 1 compression ratio, which is good for me because i want to run pump gas. By de-stroking the 340, it is more difficult to maintain higher compression ratios.
