Get the crawler gears from Injora, they come with metal pinion.
https://www.injora.com/products/injora-overdrive-underdrive-stainless-steel-transmission-gears-for-1-18-trx4m
I have the 59% underdrive (way better for crawling over stock ratio).
They now do a 32% underdrive, that maybe better if you want to do some trail driving. But I haven't tried that one so couldn't honestly say.
I run my bronco for a while with the plastic pinion. Only reason I changed it was motor swap. The injora motor comes with a stainless pinion.