What you need to do with the plots now is calculate the engine torque at various engine speeds in all gears, then plot the results over the BSFC plot to give the road curves Vs BSFC.
Then you have all you need to drive at theose BSFC points you choose
If you don't have any efficiencies then calculating the engine torques for road speeds may be a little difficult, but allowing 23% for drivetrain losses is a typical figure.
A more reliable method of getting the drive train losses is to stick the car on a roalling road and do a motored run in neutral to actually measure the power it takes to achieve the road speeds.