Use a table ban saw to hack off the 340 piston crown .

Jessearent said
My understanding is 3.31" 340 stroke subtracted from 3.58" 360 stroke equals .27" added to the overall increase in thickness. Moparpush rod is 7.5" / SBC is 7.794- 7.8". So .30" is close to .27" I will use adjustable rockers to get it spot on. Not sure where you got the .80" figure. Gonna use the 0.080" head shim combined with standard 0.038" -.040" head gasket equals .120" to startwith and then I will check my dome and see were I stand. And go from there...pushrod length really needs measured when it's close to being assembled but you get the general idea...I hope, there's a lot of heklers and unbelievers out there.

i missed a zero, lol. the point about pushrods was it's another expense. as already suggested if you sold the 340 pistons and bought some 360 pistons you wouldn't need to buy pushrods so there's your difference between the sale of the 340 pistons and the purchase of the 'right' 360 ones. plus no faffing about with spacers and the potential for leaks they can create. you said you wanted to use what you have to save money but you won't once you buy pushrods. also i think i mentioned this what about intake fitment? the same as when milling heads the intake needs machining to fit, you'll also need to 'make' more spacers now the heads are higher up. seems a vast amount of work when you'll be miles ahead just selling what you have and buying the right parts with that sale money and the money you save on pushrods (and no work making spacers, 4 of).
if you're doing it 'because you can' then why ask here?
neil.