I think I have all Pokemon in my FireRed without trading, so here is list of Johtos:
-Sentret, evolve to Furret
-Ledyba, evolve to Ledian
-Spinarak, evolve to Ariados
-Natu, evolve to Xatu
-Hoppip, evolve to Skiploom, evolve to Jumpluff
-Yanma(cannot evolve to Yanmega, gen4)
-Wooper, evolve to Quagsire
-Murkrow(cannot evolve to Honchkrow, also gen4)
-Unown
-Wobbufet (not sure if you can breed two to get wynaut)
-Dunsparce
-Qwilfish
-Heracross
-Slugma (evolve to Marcargo)
-Swinub (evolve to Piloswine)
-Delibird
-Skarmory
-Phanpy (evolve to Donphan)
-depending on starters:
Bulbasaur-Entei
Squirtle-Raikou
Charmander-Suicune
read guides to learn how to get one
-Larvitar, evolve to Pupitar, evolve Tyranitar
Other Johtos avilable(e.g. gifts,other evolutions, breeding)
Gift-Togepi (evolve to Togetic by happiness)
Other next generation evolutions:
-Crobat (evolve Golbat by happiness)
-Bellosom (use Sun stone on Gloom)
-Blissey (evolve Chansey by happiness)
*Breeding-you may get some baby Pokemon by breeding two of different gender or with Ditto, to breed you need acces to 4island, put in day care two Pokemon of same egg groups(every Pokemon has egg group info on PokemonDatabase) except egg group uniscovered(mostly legendary) and wait till you get egg(old man in front will stand step outside)
-Pichu (breed Pikachus or Raichus)
-Cleffa (breed Clefairys ot Clefables)
-Iglybuff (breed Jiglypuffs or Wiglytuffs)
-breed either Hitmonlee or Hitmonchan you get in Saffron dojo with Ditto to get Tyrogue, evolve to Hitmonlee if attack higher than defense, evolve to Hitmonchan if defense higher than attack, evolve to Hitmontop if attack and defense are same ALL hitmons evolve at LVL20
-breed Jinx that you get for Poliwhirl in Cerulean to get Smoochum
-breed Electabuzz to get Elekid (Electrivire not avilable, gen4)
So I think that's all, and I'm not sure if you could breed two Wobbuffet to get Wynaut, or get Eevee happiness to evolve to Espeon. So you can get all listed Johtos only if you beat E4 and champion once. Check listed Pokemon sites on Pokemon DB to see locations. If you have any problems or questions contact me by PokemonDB account or email.
Source(s): expirience, playing Pokemon FireRed and knowledge.
EDIT: You cannot evolve Eevee to either Espeon or Umbreon by happines, but I think it would be better if you could. Unfortunately, there is no day and night time. But, you can breed 2 Wobbuffets or 1 and a Ditto to get Wynaut, but the Wobbuffet has to hold Lax incence found in Lost cave. Also, normally by breeding 2 Marills or Azumarills (found in LeafGreen not FireRed sorry) you would get Marill, but if Marill or Azumarill is holding Sea incence (also found in Lost cave) you can get Azurill. There's a lot more of incences for breeding introduced in Gen-4 games, so you can acctualy go check for them somewhere.
