[awg]

Late to the party

Make sure the lock up torque convertor is working

Consider to fit a transmission temp gauge

Consider to fit a manual vacuum gauge temporarily

800kg on an incline will heat up the transmission a lot

You should be able accelerate on a slight incline

Was the engine run-in with good practice

Do a compression test, that will be a big clue on power

Finally, a wheel dyno will give you real numbers

I have seen a rebuilt engine should put out 200hp at flywheel, 115 at rear wheels auto trans no lockup