Can we talk you into finding a 360 block & stroking it (4" cranks are cheap nowadays) & the KB 356 (iirc) pistons ain't too bad. NOBODY that I have even spoken with that has stroked one has regretted the reasonable time/expense it takes to do one. You get alot of cubes (408) in a SB package. You have a bit invested in the 318 but I dont think you will get what you are seeking from it & once the 408 fries the tires one time you will forget all about that 318!