I've learned a lot from this project.
1. Ejection pin is different lengths in some Bolt heads
2. Axis Bolt heads are interchangeable with 10/110 series
3. If you have the old larger firing pin and a newer, small diameter bolt head, you can order the $5 smaller firing pin and it works well with the newer Bolt heads.
4. My old magnum bolt head had a cutout in the back end of it (closer to the safety). I used angle grinder to shave enough off of the newer standard bolt head to make it fit. Works well (I think). I had a hard time finding ANY bolt heads with the cutout for older flatback receiver bolts...