Snorlax
Toxic is not a good move in Gen 1 OU. Whenever a Pokemon switches, Toxic reverts to regular, weak poison. There is no way to get around that, since Spikes or Stealth Rocks dont exist yet.
Toxic is therefore, not a viable option. Substitute does not really fit well on your set. It doesn't have many uses in Gen 1. Focus Punch does not exist yet, Snorlax has no boosting moves in Gen 1 that fit on your current set, Toxic is bad, Will-O-Wisp does not exist yet, Thunder Wave doesn't have much of an impact on Snorlax's performance since it's already super slow, and all of those problems + Fire Blast burns can be fixed with Rest. In the last slot, you can use Reflect to improve Snorlax's physical bulk or Self-Destruct to KO/do major damage to anything in the way (fun fact?: I'm pretty Snorlax's Self Destruct is the strongest move in Gen 1). If you are interested, there's also a mixed Amnesia set you can use (1 Amnesia is equivalent to 2 Calm Minds because of Gen 1's Special stat.) Snorlax also is not a good lead and should be saved for mid/late-game.
Snorlax
- Body Slam
- Amnesia
- Blizzard / Ice Beam
- Rest / Fire Blast
Your other moveset should look something like this
Snorlax
- Body Slam
- Rest
- Self-Destruct
- Earthquake
Alakazam
The set is good. However you should probably use Exeggutor. Like I said in a comment, Exeggutor is the 2nd best Pokemon in Gen 1 OU, all because of STAB Psychic, a favorable matchup against Rhydon and Golem who are obstacles in the way of Tauros, Zapdos, and Snorlax due to its colossal Special stat dwarfing the rocks' pitiful 45 and 55, access to the 4x effective Mega Drain, and the deadly combination of Sleep Powder + Explosion. Exeggutor is one of the, if not the, best leads in Gen 1 OU. Starmie and Jynx are also great, but there's a reason why Exeggutor is considered by almost all RBY players to be #2.
Exeggutor
- Sleep Powder
- Explosion
- Mega Drain
- Psychic
Zapdos
Zapdos doesn't really need dual screens. Thunder < Thunderbolt, for its consistency (Thunder has 70% accuracy in Gen 1, not 90 like Blizzard does). In Gen 2, Thunder is usually better, but that's because Gen 2's metagame is focused so much on stall and Zap needs Thunder's power to get rid of some obstacles like Snorlax. Gen 1 on the other hand is a very offensive metagame. Thunderbolt is thus preferred. Drill Peck is also a mandatory option as it allows Zapdos to hit Chansey and Exeggutor, something which Thunderbolt does not do. Agility can be used in the last slot alongside Thunder Wave. It may seem weird, but it improves Zapdos's critical hit rate (in Gen 1, crits are based on Speed) and it allows Zapdos to outspeed every single Pokemon in the long term, while Thunder Wave makes Zapdos temporarily faster against paralyzed threats than with Agility.
Final moveset:
Zapdos
- Thunderbolt
- Drill Peck
- Thunder Wave
- Agility
Lapras
This set needs a little improvement. Psychic only worsens Lapras's matchup against Starmie and Amnesia Slowbro, as well as Chansey. Thunder is once again worse than Thunderbolt. Psychic should be replaced by Sing or Confuse Ray for a better matchup against Water-Psychic types and Chansey. I've noticed your team lacks a Normal resist as well as a strong Zapdos switch in. You usually need one if you don't want to get bulldozed by the big four of RBY OU. Rhydon is usually better than Golem. Rhydon and its massive Attack stat and STAB Earthquake makes it great with paralysis, which is kindly supplied by Zapdos. Its base 105 HP stat means it can create 101 HP Substitutes to foil most Chansey lacking Ice Beam, giving it a generally favorable matchup against it.
Final Lapras set:
Lapras
- Blizzard
- Thunderbolt
- Hydro Pump / Sing / Confuse Ray
- Confuse Ray / Sing
Rhydon
- Earthquake
- Rock Slide
- Body Slam
- Substitute / Seismic Toss / Submission
Chansey
As I mentioned before, Toxic is not good on Chansey, and in general in RBY. Substitute doesn't really fit well on your set. Ice Beam > Blizzard because Ice Beam's higher PP and better accuracy can mean all the difference in an elongated battle. Chansey has several options it can explore. Reflect to have a better matchup against Snorlax, Tauros, and Exeggutor, Thunder Wave to cripple, Sing to put something to sleep and essentially remove it from action for the entire game thanks to RBY's brutal Sleep mechanics, Seismic Toss for its damage, Thunderbolt on offensive sets for its synergy with Ice Beam, even Counter for Tauros and Snorlax.
Standard Bulky set
Chansey
- Reflect
- Thunder Wave
- Soft-Boiled
- Seismic Toss
BoltBeam
Chansey
- Ice Beam
- Thunderbolt
- Soft-Boiled
- Thunder Wave
Triple KO Chansey
- Ice Beam
- Sing
- Counter
- Soft-Boiled
Final slot
You should absolutely go Tauros here. Tauros is the best Pokemon in RBY OU. Great Attack stat, high speed, an incredible critical hit rate thanks to that Speed stat, STAB Normal moves in Body Slam and Hyper Beam, decent Special stat, decent bulk, effectively no weaknesses due to how bad Fighting types are. Be sure to use Tauros as a late-game sweeper to clean up the weakened opposition and spam Hyper Beam once everything has been significantly chipped.
Tauros
- Body Slam
- Hyper Beam
- Blizzard
- Fire Blast / Earthquake
