I need some advice/help !

I have a Palmetto/Garret 1874 that I recently picked up.
It has a Soule Tang sight and whomever drilled/tapped it did not get it centered.
Is there a base that I can get that will move the base to alignment ? I need a horizontal slotted base. front and rear.
The front sight is pushed way left and fully adjusting the rear I still shoot 5" left @25 yds. so at 100 I'd be way the heck off.
Is there a reputable gunsmith that I can send it to to get it fixed ?
The iron sights work perfect after I moved the front sight to center, but I'd like the ability to shoot much further and it ain't happening with what I have.
Thanks , John.

If I'm comprehending this correctly, the off center holes are in the tang. So several options exist, including welding up the holes and re-drilling them, but I think a custom mounting plate could be made to correct the situation. The plate would screw into the existing holes and new correctly centered and spaced holes drilled into the plate. Sight then mounted on the plate, with only the thickness of the plate to compensate for in elevation.

DG

Just fill the off center holes with plugs and drill/tap new ones. Then install a vernier with the proper hole spacing

Is it possible that the sight isn't standing vertically on the tang? Would shimming it on one side help?

As uscra mentioned; be sure the sight is perfectly vertical before plugging or drilling anymore holes! Your problem may be fixed by a simple shim vs. more holes. Once it's vertical, the Soule adjustment should have enough windage to fix any slight variation.

The holes are drilled to the left.
The tang has a natural curvature so the base is not vertical.
If I shim the base to vertical then the base will still be to the left and I will still need to drift the front sight to the left.
If I have an issue with the sight and need to go to irons , then I would have to drift the front sight to the right.
I am looking at going to a different style sight as I was mistaken and it is a Creedmoor style with the in/out windage adjustment and not the Soule . I researched more after posting and realized as much. I will get out my brass shim stock and see what I can do.
The suck thing is the front sight being drifted so far left.
I just put a Marbles' tang sight on a 26" Winchester model 94 and it is dead nutz on and I'm a hobby gunsmith !
I have done a lot of gunsmithing on all kinds of rifles and just take my time, this appears to be done by a monkey in a hurry !

How much to the left are the holes off? The existing can be drilled and tapped out larger, plugs fitted ( here I like to single point the threads leaving them a snug fit) locktite or soldered in place then finished down to match tang inside and out of tang. Then set up in mill and redrill holes off center in the plugs. The sight threads are probably 5-40. a 1/4 28 or 32 plug will allow for almost a .125 shift to the right.

THAT sounds like a plan!

I usually set the tang up in the mill and cut new oversize holes ( with an end mill) in the correct spot then plug the hoes with a bolt the proper size then drill it for the sight screws. Most of the time a 1/4-28 bolt works fine. I have seen quite a few where someone drill the holes with a portable electric drill and the holes walk off center.