The difference between Part 61 and 141 is that the 141 is a more structured course that includes more ground school and 3 flight orientated stage checks, usually by the chief or assistant chief flight instructor. Because of this, you are allowed to sit the final check ride with the D.P.E. or FAA examiner with only 35 hours. Whereas I believe the Part 61 requires a minimum of 45 hours.
I did a Part 141 course with no previous experience and it took me 55 hours. The average time is between 50 to 70 hours. I think you would have to someone pretty special to do it in 35 hrs.