A 245/60-15 (front) will be exactly the same height as a 295/50-15 (rear) and the 295 will be the perfect tyre for a 15x10" rim.
But I don't think a 4.5" backspace will work unless you have fender flares. You really need a 6 or 6.5" backspace to work with standard guards.
You
will need to modify/change you rear trailing arm to accommodate such a large rear tyre.
Here's a photo you can use for comparison.
Note a 295/50-15 will have a lot more sidewall bulge than the 18" tyre in this photo: