reaching 170kmph on m13a with auto tranny which is 4 speed is somewhat unbelievable...probably because alto and swift have not much difference in curb weight. maybe a maximum 100-150 kgs.
What tyres are you using? anything below an 'R' speed rating is extremely dangerous. if you intend to go upto those speeds, you should have proper tyres with good alloys...not cheap chinese ones. overall, such speeds are risky business...
but one thing for which i am sure is....the acceleration would be great...m13a is overall a very rugged engine.