to be honest, its all in your preference. Silver trucks are great they are light and durable. Thunders are ok the new hollow kingpins are unbelievebly light and for grinding get indys. If you independents are great for grinding and are on the heavy side but the new stage 10s are a little lighter. So if you want trucks that are great for grinding get indys if you want styly trucks that are good for flip tricks get thunder and if you want all around trucks get silver.
Ps dont get venture they break easily and are not great quality for grinding.
TM73 Thunder Wave can be bought at the Battle Frontier shop.
TM25 (Thunder) can be bought at the Goldenrod City Department Store for 5500 Pokedollars.
you need a pichu and than give it to bill father by mistys gym and you will get a thunder stone.
Thunder stone is not a TM, it's an item to evolve things like pikachu.
You can find it near route 15
use a thunder stone on eevee
at the pokeathon, but only on certain days
Silver
try the game corner
Show Bill's grandpa a Pichu, and he'll give it to you.
At the Pokethlon Dome or at the Bug Catching Contest
You have to get a pikachu first then give it a thunder stone, or you can train it to evolve