I shoot a pse bruin L3 at 55lb, 28 inch draw, and 29 in arrows. I am getting a dozen cabelas stalker extreme arrows spined at 65-80. I was wondering if I use a 125 grain broadhead will they be spined right?

Check the spine charts, but be aware that it's better to be too stiff than too soft (assuming you use a release, of course).

I've learned (the hard way) that the charts are pretty good for shooting field points, but aren't always good for getting good BH flight.