I will say this Weaver bases hold zero, period! There are some Weaver or Weaver style out there with rounded cross slots instead of the squared slots; I can't vouch for those, but the square cross slots are tough and hold zero/repeatable zero. There are lots of rings out there that are easier to install than the Weaver banded style.
A nice Lyman 6W recently sold for $175 on eBay. If they are complete on a 375 base they sell for $250 all day long. There is a 458 sight on ebay that started at #250 and has been reduced/relisted numerous times with no takers. I almost think about getting it and putting it on my 375 but I think the hole spacing is different. I also think that the guys who own Africans don't mess with them much, hence no need for a replacement sight to replace one that had been removed by the previous owner. 75% of the 375's for sale are missing the rear sight; I lucked out and at least have the base on mine.
As far as extractors go on pre 64's is if undamaged/unaltered it should work just fine as a drop-in. The extractor collar has a function in this operation as well. The collars do need to fit the bolt properly and exert tension on the extractor. You extractor looks damaged and/or altered.
Something to always consider on pre 64's is they were hand fit and finished by gunsmiths; they were not put together by laborers off of the street. Things like stocks and buttplates are less than 50% chance of going together and fitting as the stocks were hand sanded and then the buttplates fit and married to that stock. The barrels were also hand polished by a human and they vary in diameter.
I do not think you could go wrong with a low comb 375 with a Lyman 48 on it. There are tons of them out there with no rear sight! I once had a 375 with a Lyman 48 WJS mounted that could be left on while using a scope. I used Leupold QR bases. I had a friend mill down the top surface of the base and the torx heads a bit to where the slide from the Lyman 48 went low enough to zero and clear the scope tube.
