I would retain the 340, then later stroke it. You don't see much difference betweeb the budget 340 and budget 360. I built a .030" over 340 stroker a couple of years ago, stroker kit was 1200 at Muscle motors, adjusted the quench, homeported the heads and installed a comp cams flat tappet XE 285 cam and that's about it with some attention top details. Factory intake, factory exhaust manifolds etc. 416 cu in with very civilized manners, 9.5:1 CR, made 410 hp through original exhaust and 440 with 1 5/8" primary headers and 2.5" duals. Should relatively easily run sub 13 sec et's even with a compromise gearing and converter and look stock.