OK, In an effort to bring this back on topic!

My figures from the graph are;

RPM BHP lb/ft
1500 47 160
2000 70 175
2500 92 185
3000 110 195
3500 130 200
4000 158 200
4500 180 205
5000 200 205
5500 225 205
6000 240 200
6500 260 200
7000 270 200
7500 270 190

I did this nicely with a square, and dividing the axes scales in half, the numbers are the nearest approximation I can make out.

From 3500 to 7000 there is no more 5ft/lb difference in the torque curve.....nice.