[Bongo Boy]

Any other requirements other than it have a long slide and an ambi safety? If no thumb safety is an option I'd recommend looking into building a Glock 20 longlslide--but that's not an inexpensive option. It does give you what appears to me to be about the strongest, fully-supported chamber option I'm aware of: heaviest chamber and barrel, beefiest slide, etc.

I'm sold on the EAA Witness Hunter for a more traditional 1911-style, all-steel 6" gun. Beautifully built and finished, and a well-supported chamber. I like all-steel, and I like the double-stack configuration with a grip that is super comfortable even for average-sized hands. I'm not a hunter, but if the gun is for hunting then I can't imagine how the double-stack design of the Hunter would be of any real attraction. In that case, I'd probably go Fusion and just pick one their many longslide models.

I think these two options will total out in the same neighborhood--but with the Witness probably being less (at $1,100 or so) that the longslide Glock route. If you want optics, then your available options might change the total build cost comparision quite a bit.