Yes it will fit. I have an fmf header with a wb slip on. As far as the tusk nerfs Im not sure. I know when I got the ac nerfs I had to get the pegs. The ac nerfs mount to the pegs. It all depends on how the tusk bars mount.
Tusk bars bolt to your stock pegs the same way the heelguards do if that helps, if you can use the stock heelguards with the ac pegs then most likely it will fit.