Do both rifles have the same barrel length??
If you've got a shorty M14 with a low front sight blade, I can just about guarantee you'll be shooting way high. I had a M305 professionally shortened to 18.75" barrel from 22", and tried to hit targets with the original sight.
The shorter front sight is intended for the longer barrel, while a tall front sight is needed for the short barrel rifle. On my rifle, the sight radius was changed when the barrel was shortened, which is why I needed a taller front sight.
I managed to find a tall front sight in Canada thanks to a CGN'er, but I do believe that Brownells has them and will ship them to Canada.
Of course, you could always mount a scope on the short rifle with the low sight and forget about the front sight.....