Today, dollar for dollar, is the 318 faster than the 340 ???

........But for how long? Seems like you did the basics to the 340 to make it a solid runner. You are right though, if you just slapped on $2800 worth of go fast goodies onto the 318 it would move. But you'd still have old worn out heads, old oil pump and old rings. JMHO.
For 2800, you could put aftermarket aluminum heads, with 030 pistons, etc.