While I'm no expert on Savage 99's, I've been reading up for around three years on the history and have only had mine for a year. Reference whether it is factory tapped for scope rings or not, if your rifle has 'Savage Model 99' rolled on top of the receiver ring and has holes tapped into the roll marks, it would have been non-factory. Savage sometime in the fifties, factory tapped a lot of 99's and rolled 'Savage Model 99' on the left side of the receiver ring. A lot of 99 shooters back in the day used for the most part a Stith Brand scope mount which used pre-tapped holes on the receiver tang and a special insert that held the front of the scope mount in the rear sight dovetail. The 99 I bought had such a mount, no longer made, pricey to buy. The 99 I bought from a shooter acquaintance already had the Stith on it and a older Weaver vintage scope on it.
Tried to enlarge your picture, but couldn't see enough detail. The recoil pad isn't factory, the only ones they put that style of a heavy pad on was some .358 and .375 caliber 99's Savage called their 'Brush' guns. Most all had steel or hard rubber shotgun style butt pads. The length of pull from what I've read should be 14". You could measure what is on the rifle to the end of the wood and see how close it is to that. If someone cut the end of the stock to accommodate the thick pad, the LOP would be short the 14" by at least 3/4" to an inch I'd estimate. If you've never shot a 250 Savage, they aren't a shoulder killer. Mild shooter, that recoil pad will make it like shooting a BB gun. I see the rifle does have a 'Schnoble' style forearm. These were used mostly in pre WW2 99's, although there was at least one post WW2 model, the EG that had a Schnoble tipped forearm. Savage 99 Models over the years had a lotta changes in style of sights, forearms, style of stocks, barrels, etc. Almost need a book to figure them out.
A good website unless you already are aware of it is-- Savage Shooters.com, click on the Vintage Savage section. A lot of 'stickies' with history and info on the 99. Two of the moderators, JBaker and MadDog are really well informed on the 99 with a lot of posts on the 99's history and shooting by them and other members. Info and links on the website can help ya ID your rifle as to year made and model. Two books that are invaluable for the 99: 'Savage 99' by David Royal (which I have, still in print, not real pricey, ton of info and colored pictures) and another one out of print due to passing of author, 'The Ninety Nine' by Doug Murry. Older than Royals book, black and white pictures, according to readers has a ton of information, a lot of which was taken out of Savage catalogs, written before the advent of the internet. Murry's book tends to be pricey if ya can find it, have seen it upwards of $100 plus. Both books are held with the esteem by Savage 99 fans as John Henwoods book on the Rem 8/81 does. The Savage 99 like the 8/81's are real nostalgic rifles, taking me back to when I was 12-late teens, pouring over old Outdoor Life, Sports Afield, and other magazines of the day, showing pre and post WW2 hunters with both styles of rifles in some hunting camp or bagging a nice buck or other game. Hunter would be wearing high topped lace boots, wearing red and black plaid wool jacket and similar hat. Love the old gun ads showing hunters with both the 99 and 8/81 rifles. I'm not nostolgic enough though to wish the return of 8-track music tapes or VHS movies!