"the tire sizes are 215/65r15 in front and 275/50r15 in back"
If you look at the #'s (65)-(50) that relates to the "stance or width" of the tire as its body leaves the rim.
A 70 series tire will follow straight off the rim with a small belly, ( a narrow tire) and the 65 series will have a fatter belly and be wider than the rim. Same as the 50 series, That is a wide tire,You have to get rims to suite the tire as well.
Although you can install a 50 series tire on a 65 series rim. It will just stand taller and requier less air pressure to (flatten) out the rideing surface of the tire.
Now the biggie. Is it a deep dish rim for the rear? center/center or pretruding center? That is going to be an issue there.
My best advice is go to your buddies and stick one on for good messure.
Then youll know by sight. If your happy, switch um out and give him his cash.