I wouldn’t be so quick to replace the front sight post with a taller one without first going to the range and trying to sight it in.
I have a Bushmaster barrel without an “F” mark. I purchased a taller front sight post thinking I would need it. When I went to the range the factory front sight post sighted in just fine.
I would check with G&R first. They may have some other stuff you can’ t live without. If not I think I got mine from brownells with bunch of 1911 stuff to make the shipping worth while.
I’m with Zappy my Bushmaster (without an “F” mark) was dead on after I put my BUIS on. If you haven’t shot it do that first. Then if you need one I would go to Grant.