http://www.ft86club.com/forums/showthread.php?t=15007
http://www.ft86club.com/forums/showthread.php?t=7535
https://www.ft86club.com/forums/showthread.php?t=58908
For a simple answer, between a 245/40 and a 275/35 sized tire. You don't need a spacer, but you may get rub at full turn lock left and right. Check the links I've posted and reply after reading at least 10 pages worth of posts from each
The first number in the tire size is width in mm. Second number is the percentage of the width that it is tall. So a 275/65 will be a monster truck tire compared to a 205/65. Ok, read on