W2 heads on a 318

Bore notch?

Not needed.

Total width of the valves is 3.65 minus the distance between them. I'd have to measure mine to know for sure. I'll take your measurement as a good one.

However, it isn't enough to cause an issue in a .030 over 318 which is now at a 3.94 bore. There is enough area left over there not to worry about.

Any valve shrouding issues of serious concern are more so in the cylinder head, if present. And they should be taken care of.

You have more worry about nothing than needed. MoPar didn't seem to mind it and recommended the W2 in there "Speed Tips" list on the (IIRC) 10.90 "Super Street" package. A 2.02 is recommended in the 12 second zone tip section.

Of course, if you feel the extra work is sorely needed where the MoPar engineers and drag racers didn't, have at it and run while grinding away.