Sounds like a fun build, but I would vote for a 4" crank as well. A cast mp or scat crank would work well and they only cost about $350 and add 50 cubes. It would make more power and be much more reliable.
Another thing to add is that for bracket racing the high winding sb can be a nightmare to keep consistent et round for round. They are more sensitive to atmosphere conditions and shift points.
A stroker will also be much less sensitive to gearing and stall. As for these thoughts the op can take it or leave it.
A high winding 318 would be fun, but much less reliable and more expensive in the long run.