3rd Gen Which Pokemon should be the sixth member of my FireRed team?

I'm using;
Charizard
Raichu
Alakazam
Tauros
Lapras

Which Pokemon should I choose for the last member of my team?

You should definitely get Dragonite! :)

Your team features mostly Pokemon that rely on their Special Attack stat, so how about a heavy physical hitter? I'd go with either Dragonite or Machamp. Have fun :).

I'de sy Riachu .. your gonna need a electric type ... Dragonite is way to hard to level and it's moves aren't good at all until you get up hgh enough so ... I would recommend Riachu :)

oops! didnt see Riachu in the list my god XD yeah then get dragonite haha

If you have the patience to wait after the E4 to get your final member then get a Tyranitar or Heracross. If not then get either Dragonite or Snorlax.

You should've caught a mankey in the beginning of the game. Fighting pokemon are always usefull and primeape is one of the best.

Sandslash. nuff said.

Once he gets slash he starts owning, in blue at least... idk bout FR

If you want a grass, go for Vileplume. Either that or Marowak, both are very underestimated in terms of power.
Vileplume has great SP. Attack and a great movepool, Marowak when equip with a Thick Club can deal some serious damage with Physical based moves.

I'd get a Hitmonlee or Jolteon. Hitmonlee i found recently is amazing in those games and Jolteon has amazing speed and special attack.

I think you would benefit from a solid Flying pokemon, Pidgeotto.

i'd kick off tauros and get a dragonite and maybe a grass type pokemon like victreebel

You need to catch any Fighting or Electric type.

This should have been locked way back when.