340 Street Build
that'll be a little lopey for a 340 street car, but you've got a 4spd to back it up and with those current SCR numbers i'd say the compression as well.
personally, i'd tear it down and see what cam it has and make a determination from there. if you have a stock cam, that's a big jump. if you have say, a 268 then not so much.
anyway, once you've got it apart you can see where the pistons are at in the hole, then CC your heads and determine the direction you want to go.