If you just want to increase rotor size to 14", it may just make sense to keep the kit you have and just buy new rotors. Then all you need to sell is your 13" rotors.
To do this you just need the (4) longer 3.15" caliper bracket studs (vs. your current 2.5") & the (4) .42" spacers that go onto the studs that space your caliper up correctly over the 14" rotor. Then of course the rotors.
I did not see the spacers offered through Summit, but could get from Wilwood. I may have some laying around as well. If I do I will mail to you if you decide to go this route... or I believe a stack of 3/8" AN washers works the same.
http://www.summitracing.com/parts/wil-230-9079
http://www.summitracing.com/parts/wil-160-8397-bk
http://www.summitracing.com/parts/wil-160-8396-bk
Jay