I thought helicoils were used basically when you stuff a thread and it gives you a new thread, not to make a thread smaller?
Anyway I got the bolts from a fastners place but I got 50mm bolts and that doesn't include the head so it's about 58mm not 48 that I need so I'm going today to get the 40mm bolts which should be right.
edit: Got my bolts now, M14 x 40. just need to get some brake pads and a 14mm drill bit and I should be all set!