Bicycle Tutor

I have an old trek that I'm fixing up (mostly just to learn how to do all this stuff myself). Trying to replace old cantilever brakes with new v-brakes but the spring pin doesn't fit into the hole on the frame brake housing. The front brakes fit but the rear brakes do not. Any tips would be great.

Is the hole to small or not in the right position?

The hole is not in the right position. the spring is a bit too big (diameter) - just missing the hole by a couple milimeters to the outside.

If it looks O.K then I would consider drilling another hole or opening the existing one?
Option 2 would be to bend the spring to suit. It's funny that the front one fits but not the rear.
Try the rear one on the front as I don't think it matters whether fitted to front or back?
Not sure of the spring shape but it is the correct spring? or the right way round ?
I had no trouble with mine when I swapped to V brakes from Canti's.