Pretty much what the title says, I have a savage 10FP in .308 and would like to swap it to .223. Is the barrel and bolt face lug all I will need to change? I know barrel will need to be headspace but is there anything else I’m missing?

You will also need a 223 bolt baffle as well.

If it’s a detachable mag then either 223 mags or just bend the feed lips of your 308 mags to hold the 223 cases.

No. Don't bend .308 magazines in an attempt to use it for .223.

I think the OP is taking the long way around the barn. If you want a .223 Savage rifle then buy one. Sell the .308 to help finance it. What you are proposing is a complete rebuilding of your current rifle.

Savage actions are available with the proper bolt if you want to build a .223 from scratch.  

I get it— that’s the standard arfcom answer: “get both/get another one.”  However, the draw of Savage rifles is the easy ability to do things at home—swappable bolt heads and DIY barrel changes. I can swap calibers on my Savage in less than 30 mins, including perfect head spacing.

Of course an easier to swap setup is to buy a dedicate bolt set up for .223. Or buy a .223 rifle, as you stated.  But that’s not what OP asked.