[Closed] Road Brake Caliper help required

I just bought a new groupset for my road bike Shimano 6800 ultergra 11 speed. I swapped all the parts over no problem with the plan to put the 5700 10 speeed groupset on my winter bike. All went fine until I went to fit the front brake on my winter bike. The problem is that there is not enough drop on the caliper for the pads to contact the rim.
So I went to buy a new caliper with a longer drop, thinking there would be 2 options short or long. Looking on CRC they have a choice of front and rear but both say that the drop is 49mm. What is the difference between the front and rear calipers? How do i know what length of caliper to buy? It only needs to be about 5mm longer than what i have.
Stupidly i binned the old brakes before double checking everything fitted!

Cheers folks