Bid you welcome...
Turbo--First of all, welcome to the club! I'm sure you'll learn a lot here (I sure have!) but also be ready to share your own shooting-related knowledge & experience--everybody's an expert on
something!
FYI, the Stoney Point Overall Length Gauge is now called the Hornady Lock-n-Load Overall Length Gauge. Hornady bought the rights to it some time ago. Hornady hasn't changed anything about this device AFAIK, so if you have some parts of it from Stoney Point they still should work.
Midway USA doesn't list (Midway Catalogue #33) the modified case you need in .300 Savage. That could mean it's not made, or just that Midway doesn't choose to carry it. Or perhaps they'd have one but not put it in their catalogue. I think some 'phone calls would be in order--Call Midway and see if they have that case, if not, call Hornady and see if THEY have it, or if they'll make you up one special (pricey but as a last resort, better than nothing!)
Midway: 1-800-243-3220
Hornady: 1-308-382-1390 or 1-800-338-3220
I would call rather than writing or e-mailing, and ask to be connected to an expert if the salesperson can't help you. There's something about a live person on the 'phone that brings out a better, more complete response than does a piece of paper, IMX.
Oh, FYI again, I used 3 acronyms that get tossed around a lot on this forum. If you're not familiar (and forgive me for mentioning it if you are):
FYI = For Your Information
AFAIK = As Far As I Know
IMX = In My Experience
Anyhow, good luck in your quest, and once again, welcome to the forum!!