Nathan,
I'm not sure this is accurate in all Savage cases, but here's is what I did, and why, on a Striker.
The Striker started as a 22-250 (standard bolthead) I went to a 6.5 wssm ( mag bolthead). I tried the only magnum bolthead I could find, a LA magnum one. It wouldn't go because there is an indentation on the inside of the bolt body on the short action and a corresponding inlet on the bolt head, the LA didn't have this inlet.
I wound up sending the LA bolthead to a smith to have the inlet milled in to it. After that it fit and functioned perfectly, cost me $50 buck about 4 yrs ago.
I'm not sure if all SA bolt bodies and heads have the indent and inlet or not, but at the time it was the only way I could find to get a push feed mag bolthead on a SA bolt.
You might want to PM geargrinder or hammertyme on this site, those to gents have forgotten more about Savages than I'll ever know.
Chris