I believe that the 35th's came with 17 in wheels, which used a 215/50 tire.
300 pounds
my tire sizes for my cougar are P215/50R16 or go here so you can find your size http://www.dragtimes.com/Mercury-Cougar-Tires-m31-n237.html
They are 5"x7" front ant rear, http://www.modifiedlife.com/1991-mercury-cougar-car-audio-wiring-schematic/
According to one of Fords websites : For a 1969 Mercury Cougar ( all factory available engine sizes ) ( .035 inch spark plug gap )
all speakers are 5"x7" - its a special size for cars made by ford motor company
The 2000 Mercury Cougar (V6) came equipped in two tires sizes of 205/60/15 and 215/50/16. The offset and backspacing vary by wheel type (factory or aftermarket). The bolt pattern is 4-108 for this model.
According to the 1997 mercury Cougar owner Guide : ( 5W-30 is the preferred oil for the 3.8 litre V6 and the 4.6 litre V8 engines ) ( With engine oil filter change , 4.7 litres / 5.0 U.S. quarts of 5W-30 , both engine sizes )
According to my Chilton's Auto Repair Manual : With engine oil filter change : ( 5.0 US. quarts for all factory available engine sizes )
6x8.
318 in my 1971 Dodge Charger Special Edition
Your correct tire size is on your door sticker.
Tire sizes are on the door jamb sticker.