If it helps, here is a picture of the angle of the gearbox mated:
Make sure the engine is rigidly supported in its normal position. It want to tilt back with the gearbox removed. After that, I found that I needed to elevate the other end of the transmission. I used a the wooden piece on the jack and slid it back and forth to achieve the right angle as determined by the 4 bolts/guide pins.
Good luck