This team is made with the restriction of only being allowed to use Pokémon with movesets you can obtain on the Gold/Silver/Crystal cartridges, but should function reasonably well in GSC OU. Without further ado, here is the team:
Snorlax@Leftovers
Return
Curse
Belly Drum
Rest
Snorlax may or may not be my lead, since most other things (bar Forretress) seem unsuited for the role. This is the relatively uncommon CurseDrumlax. Body Slam is possible in the place of Return, if you value the paralysis chance. Double-Edge is not, as it is a Gen 1 TM. If Skarmory becomes a problem, FB Curselax is another option.
Tyranitar@Leftovers
Rock Slide
Pursuit
Fire Blast
Roar
This is an important supporter for Snorlax. Fire Blast takes care of those pesk Steel-types that will happily wall Snorlax, while Pursuit is for Gengar and Misdreavus. Rock Slide for STAB, and gives this team an answer to Zapdos, Roar since this team has no other Phazer. Tyranitar is often the most unpredictable Pokémon in GSC when it comes to movesets, but on this team, all four moves are essential.
Forretress@Leftovers
Spikes
Rapid Spin
Explosion
Hidden Power [Bug]
Spikes, Rapid Spin and Explosion in one neat package. Forretress has nice synergy with Tyranitar. Hidden Power [Bug] is a semi-decent attacking move that keeps Starmie out of its face, but if Starmie is not a problem, this could be changed to Toxic if you want. Hidden Power [Bug] is likely the best option anyway.
Misdreavus@Leftovers
Mean Look
Perish Song
Protect
Thunder
Misdreavus is a spinblocker, but also provides offense. Thunder gives me another option against Skarmory, but is less reliable than Tyranitar's Fire Blast. Perish Trap has the possibility to break stalls. Walls mono-attacking Snorlax and can take predicted Explosions.
Miltank@Leftovers
Body Slam
Growl
Heal Bell
Milk Drink
Provides Heal Bell and an answer to Snorlax without Belly Drum. Tyranitar in particular appreciates Heal Bell support, as it is very vulnerable to Toxic. Spreading paralysis with Body Slam is useful. Miltank is a good teammate for Snorlax as well, as it can paralyze Normal-resists coming in to wall Body Slam, and Heal Bell synergizes with Rest.
Heracross@Leftovers
Megahorn
Earthquake
Rest
Sleep Talk
The last slot goes to Heracross, but if you have better ideas, they are very welcome. Sleep Talk Heracross has a bad match-up against Flying-types and a fairly good match-up against everything else. It is a good status absorber, but this doesn't synergize very well with Miltank.
Closing thoughts: No Electric, since finding Raikou with the correct DVs is hard and finding Zapdos is impossible. As a result, if Tyranitar and/or Misdreavus are out of commission, Skarmory will walk all over my team. Heracross should probably be thrown out for something else, but it's hard to say what, given the cartridge restraints.
Snorlax@Leftovers
Return
Curse
Belly Drum
Rest
Snorlax may or may not be my lead, since most other things (bar Forretress) seem unsuited for the role. This is the relatively uncommon CurseDrumlax. Body Slam is possible in the place of Return, if you value the paralysis chance. Double-Edge is not, as it is a Gen 1 TM. If Skarmory becomes a problem, FB Curselax is another option.
Tyranitar@Leftovers
Rock Slide
Pursuit
Fire Blast
Roar
This is an important supporter for Snorlax. Fire Blast takes care of those pesk Steel-types that will happily wall Snorlax, while Pursuit is for Gengar and Misdreavus. Rock Slide for STAB, and gives this team an answer to Zapdos, Roar since this team has no other Phazer. Tyranitar is often the most unpredictable Pokémon in GSC when it comes to movesets, but on this team, all four moves are essential.
Forretress@Leftovers
Spikes
Rapid Spin
Explosion
Hidden Power [Bug]
Spikes, Rapid Spin and Explosion in one neat package. Forretress has nice synergy with Tyranitar. Hidden Power [Bug] is a semi-decent attacking move that keeps Starmie out of its face, but if Starmie is not a problem, this could be changed to Toxic if you want. Hidden Power [Bug] is likely the best option anyway.
Misdreavus@Leftovers
Mean Look
Perish Song
Protect
Thunder
Misdreavus is a spinblocker, but also provides offense. Thunder gives me another option against Skarmory, but is less reliable than Tyranitar's Fire Blast. Perish Trap has the possibility to break stalls. Walls mono-attacking Snorlax and can take predicted Explosions.
Miltank@Leftovers
Body Slam
Growl
Heal Bell
Milk Drink
Provides Heal Bell and an answer to Snorlax without Belly Drum. Tyranitar in particular appreciates Heal Bell support, as it is very vulnerable to Toxic. Spreading paralysis with Body Slam is useful. Miltank is a good teammate for Snorlax as well, as it can paralyze Normal-resists coming in to wall Body Slam, and Heal Bell synergizes with Rest.
Heracross@Leftovers
Megahorn
Earthquake
Rest
Sleep Talk
The last slot goes to Heracross, but if you have better ideas, they are very welcome. Sleep Talk Heracross has a bad match-up against Flying-types and a fairly good match-up against everything else. It is a good status absorber, but this doesn't synergize very well with Miltank.
Closing thoughts: No Electric, since finding Raikou with the correct DVs is hard and finding Zapdos is impossible. As a result, if Tyranitar and/or Misdreavus are out of commission, Skarmory will walk all over my team. Heracross should probably be thrown out for something else, but it's hard to say what, given the cartridge restraints.