You'll have to basically do a complete BX to ST conversion if you you're wanting to change the arms out (shocks, turnbuckles, shock towers, arms, etc...)

I'm actually in the process of putting ST wheels on my BX... I'm hoping it won't be quite so squirrlely on bumps. For the front just change out the knuckle arms to the ST's as well. I bought a set from one of the ebay sellers that part out evaders (nitro's works as well). I believe for the rear tires they just bolt right on. I got new rear tires last week and going to get the rims sometime in the next week or two, whenever I find the time to sit down and order them. I'll probably need to regear it for the added weight as well, but I'll need to do that anyway as I want to get a new motor too.