I used Art Morrison for my 10 point kit in my Dart.
I used a Competition Engineering kit for the 6 point I had in our last car.
And if I do another , I will have learned enough to do it better than the last one.
Hindsight tells me I should have gone through the dash and created much more room to get in and out of the car.
But if I did go that way , I would seriously consider an experienced fabricator to do the job for me.
My welds are Dog's Butt ugly , but I trust them.
I use mild steel so I can MIG it , but the tight quarters and awkward positions required were much less of a problem , even in my 40's.
That was twenty years ago.
It's not the place to learn to weld , that is for sure.
And you can save a lot of money by mocking it up and doing the fitting your self if you are going to have it welded by a pro.
The guys I use for stuff I can't do are around 100.00 an hour and well worth it.
And the fitting is the time consuming part of the project.