Here's the history:
Hi Std started in Connecticut before WWII. The models you are referencing are post 1950 guns. Hi Std was forced from their Hamden CT factory in the 1960's when they had financial trouble after loosing their Sears contract. They continued at the smaller East Hartford factory until the early 1980's when they closed their doors. The name was purchased along with all the engineering drawings and I think the manufacturing apparatus (jigs, etc). A new Houston Texas High Standard Company opened there in the late 1980's or early 1990's. Theses are the "Texas" Hi Std's. Today they make fine clones but their early examples left something to be desired. For any Hi Std repairs or parts or service I would contact them directly:
After the Connecticut Hi Std closed its doors one of its executives had some stainless clones made under the Mitchell name but not in the Texas Hi Std Co. plant, which started a lawsuit. Stoeger also had some clones made in Texas and was sued too, as the TX Hi Std Co. owned the name. TX Hi Std won the law suit and the Stoeger and Mitchell clones disappeared from the market place (Mitchell still exists but makes phony so called "collectable" Mauser K98 rifles).
In this post 1950 era, Hi std made several variations identified by their grip angle and the mechanism to remove the barrel. There were slant grip guns, Military grip guns, lever takedown guns, button takedown guns and finally screw takedown guns. They made variation in finish, details, and for various usages (match, field use, and plinking). Some of the model names are Citation, Tournament, Trophy, Victor, Sport King, Field King, and others I can not remember at this time.
I believe today's TX barrels come pre-drilled for a scope rail. But if I were you, I'd look at the web page, then call them to explain what you want. They can tell you if the front sight is removable on their barrels or the one you currently have. On some Hi Std's the barrel just drops on (assuming you get the one for your exact model) but some have to be fitted. TX Hi Std can fit a barrel you buy from them and maybe even some older Connecticut barrel (??).
The guns to steer away from are Mitchells, Stoegers (both are not the equivalent to real Hi Std guns), the screw takedown late Connecticut guns (??) and early TX Hi Std guns (I recommend only the latest TX Hi Std stainless framed gun as the earlier blued frames have had some terrible problems over the years.
The guns to have are the Hamden CT guns first, the East Hartford CT guns next (except for the very last screw takedown guns, which are better avoided as the quality MAY be suspect), and todays TX Hi Std guns (not earlier blued framed versions). The pricing of used guns reflects this order. There, of course, are exceptions to these recommendations but collectors drive the pricing so finish is super important for pricing. For shooters nearly all CT Hi Stds shoot with the same excellent accuracy.
Here's a hint: Keep a good standard recoil spring in the gun at all times and only shoot Standard Velocity ammo. If you don't, you can eventually crack the frame on Connecticut guns. Supposedly (??) the new TX guns are immune to that cracking due to materials changes in the frame.
I included a lot of info here, not knowing where you were at in your Hi Std knowledge. Sorry if it is too much.