Need 2 other Pokemon for my team (LG/FR)

Hi, in Leaf Green, I have 4 Pokemon and have started Silph Co.
I have a Lv. 40 Venasaur (Strength, Sleep Powder, Leech Seed and Razor Leaf), Lv. 42 Vaporeon (Surf, Shadow Ball, Quick Attack, Aurora Beam) , Lv. Lv. 40 Fearow (Fly, Drill Peck, Aerial Ace and Mirror Move), and a Lv. 40 Sandslash (Dig, Brick Break, Cut, Rock Slide). I need two other Pokemon.
I've considered Magmar or Ninetails (preferably Magmar because it learned Flamethrower by leveling up) as a fire type, and Magmar could learn Psychic to cover that type. I can wait until Mt. Ember. I've considered Magneton for an electric type but I don't know if I really want it. I would like a good psychic or ghost type but at this point, I don't have many options.
Any recommendations would be taken gladly.

Ninetales is bulkier and faster, but Magmar is stronger. Also, Vulpix learns Flamethrower at level 29, but Ninetales doesn't learn it by level. Magmar, on the other hand, learns Flamethrower at level 41, but until then, it has Fire Punch, which is also pretty good. Besides, like you stated, Magmar can learn Psychic, so you should go with Magmar.

As for Magneton, you should get one with Magnet Pull, unless you really hate OHKO moves.

Magneton does sound like a good electric-type, yeah. Another one you could consider is perhaps Electrode; it's extremely quick, so if you have it trained well enough, it would always strike first and wind up taking opponents down before you even know it.

If you'd like you choose some psychic-type, you should try getting your hands on Alakazam, if possibly; it has gargantuan offensive stats, and could take opponents down pretty swiftly. Its defenses might not be that great, but this is in-game, so they're not very important, anyway. If you're going for ghost, then Gengar would be your best option.

Gengar is a really good choice for your team. You can teach him Thunderbolt if you don't want to spend too much time looking for a good electric type; he isn't weak to any of the types you'd be using electric attacks on and he has good Sp. Atk and Spd stats.

Pick him up and then get yourself a Magmar or my personal favorite an Arcanine. If you go with Arcanine though, be certain not to evolve him until he's level 49. That way you get Flamethrower and Extremespeed, two moves you will want him to have. I'd teach him Dig as well to cover his electric weakness.