I'm building a drift car for myself, but I don't know how to do the transmission issue. The engine of my vehicle is Toyan Engine L200. Do you recommend a gearbox for drifting? What do you think about driving my car with rear wheel drive?
That engine is more of a show-piece designed to be a functional mini four-stroke, it does not have favorable power output characteristics for a drift car. A gearbox will be less useful for drifting because it'll give you less control over wheel speed and traction.
It can be done, but it wouldn't be particularly fast.
I think you may want to start by getting a normal nitro car going and seeing how it drifts, and how you could modify it.
I have a feeling that the project you're describing is a bit more ambitious than you realize- I too once dreamt of building a Toyan-powered onroad, (especially now that the L200 is under $200, which is amazing for what you get), but after I got past the "dream car" phase and began parting out a basic design, I realized I just wasn't going to wind up with what I was hoping for, not without substantially more effort than would have been worth it. Check out JohnnyQ90's youtube videos, he's built multiple vehicles around the Toyan engines, even their V8, and you'll see in his videos just how much work it takes to produce something that's more akin to a museum showpiece than a basher you'd take to the park for fun.
It was always a little interesting to me that RC plane four-strokes never really make the leap to surface vehicles, considering how much early nitro cars and trucks were powered by adapted plane engines. The OS FS-26C and Saito FA-30S-C are the only examples I can think of, both of which are basically "unicorn" engines now in terms of rarity and price.