okie dokie. after careful inspection,making sure there is absolutely no ridge of any kind at the top of the bores, new pistons/old bore should work fine.
as for running and how much HP, if your actual compression ratio comes in anywhere near 9.5 to 1, with all the parts you have stated,and sticking with only your original questions, 350 or so on a good day. should have decent torque down low,lumber/slobber it's way through the mid range,actually start moving up about 4000 rpm when it starts running out of steam,and absolutely eating gas,and spark plugs.
balance won't be affected,since it won't pull hard enough on either end to have to worry about it.
you asked.....................slap it together and enjoy