you CAN... but its not recommended. some shops wont put them on too small of rim for the fact of them breaking a bead or something and coming off. about 8"-10" wide wheel is recommended for 12.50. plus stock rims are sucked in so you will rub.
They'll fit. Stock rims are 7" wide. Its not ideal but it will work. Make sure to play with the pressure to get the best wear and ride. A lot of members have ran that exact same combo before with no issues.