Most of the T100s that I've come across were using P series tires fer stock. I know my 1993 SR5 were supposed to have as stock the 215/75-15 tires. I currently run the Yokohama Geolander A/T-S 235/75-15LT tires...really nice and smooth on the road. 
I run my tires at 40lbs fer the front and 45lbs fer the rear...but I have LT tires. It all depends on how soft you want yer ride. I can't tell the difference with my road travels at all.
Plus Zero 225/75-15 255/70-15 265/70-15 30/950-15 31/1050-15 32/1150-15
Plus One 265/75-16 275/70-16 285/75-16
Plus Two 255/65-17
Here's one of the more popular tire size calculators on the web...
I run my tires at 40lbs fer the front and 45lbs fer the rear...but I have LT tires. It all depends on how soft you want yer ride. I can't tell the difference with my road travels at all.
Plus Zero 225/75-15 255/70-15 265/70-15 30/950-15 31/1050-15 32/1150-15
Plus One 265/75-16 275/70-16 285/75-16
Plus Two 255/65-17

Here's one of the more popular tire size calculators on the web...