408 stroker engine build

You said that you didn't want to deck the block but would bore it. The cost to deck block is minimal once it's cleaned and at machine shop. Decide what compression ratio you want for the heads and deck to zero deck height or something close. Spend the money on block and the base of engine and save on intake and parts that can be upgraded easily later.
If you use your existing heads with bigger chamber go with lower CR and then you could change heads with smalller chamber later and get higher CR. I have a 360/408 that made 520 hp with 10.5 CR and runs on pump gas 91 octane. It idles well and has great torque. Makes peak HP at 6000 rpm. Cast crank should live at 6500 rpm and lower. or with liss than 500 HP. Good luck with decisions.