Picture of 340/360 head porting....Mistakes?

Well...... I would start by getting the throat closer to 90% of the valve(your average is 85% now), and flattening(side to side) & laying back the short turn.

As I said earlier, I’ve never found any success with that heavily rounded floor shape.

Even on stock Pontiac heads, that have the floor pretty rounded like that from the factory..... I’ve had success buy broadening that area.