Rear sight for non F-marked FSB

So I just picked up a 14.5" Colt SOCOM barrel and it is not marked with an F. The brown truck o happiness has not gotten here yet.

1) if it isn't marked, might it still be an F-height? How can I tell?

2) if mounted on a flat-top upper, what would be an appropriate BUIS choice?

3) Can I just replace the front sight post, or will it stick past the protective ears?

Thanks