Well, because both Gligar and Totodile will tend to lose against Ferroseed, why not include a couple of Pokemon that can beat it?
I support Blarajan's Mienfoo for the third slot because it provides the team with some bulk while still retaining some power. However, this team would be entirely physical and dedicated walls will be able to handle them relatively successfully.
So, I propose we use Magnemite to focus on enemy Ferroseed and provide a strong special attacker. It has great synergy with Gligar, and we could always throw in something or other to handle Water-type attacks from Chinchou. So,
Magnemite @ Life Orb
Trait: Magnet Pull
EVs: 240 SAtk / 240 Spd
Modest Nature (+SAtk, -Atk)
- Hidden Power [Fire]
- Flash Cannon
This should work well against Ferroseed, as well as some other Pokemon that cannot do much to it (non-Heat wave Murkrow, for instance). With a Substitute up, it can inflict massive damage to anything that doesn't resist these moves (aka just Chinchou).