The original Pearson 36 was built from 1972-1976. The Pearson 36-2 was built from 1985 - 1991. These are completely different hull designs. The P36 had a skeg hung rudder and drew 6 feet, and the P36-2 had a spade rudder, and a choice of fixed or swing keel.
First year P36-2s were predominantly fixed keel with a 6.5' draft. Most of the swing keel P36-2s (4.2' draft) were built after 1986. A few P36-2s after 1988 were equipped with a wing keel, and had a 4'9" draft.
The Pearson 35 was built from 1968-1982. All of them had a swing keel and draw 3.8' with the board up.
Best to find out which YEAR that the boat was built (it will tell you which model you're dealing with), and then determine the draft. The model year is indicated by the last two digits in the HIN.