I have done 2 exhausts through the body like this. I will tell you right now you do not want to attach it directly to the body, I think the silicone coupler might even be too much attachment, the noise will resonate through the body. The way that I ended up doing both was to isolate the tail pipe/exhaust tip from the rest of the exhaust with a flex coupling like this...
...and then using several rubber isolator hangers to steady the tip in the hole. That was the only way I could get the noise down to an acceptable level for my customer.
You will have a lot of exhaust movement on a side exit, more then straight out the back, so you will need a considerable amount of flexibility in the exhaust especially on a very short system like you are going to end up with on a Bronco. I have seen several exhaust systems that broke hangers and tubes when the tail pipe/exhaust tip is held rigid and the engine is free to move on the mounts.
If the truck isn't going to be driven much (show car style) then there are a lot of easy ways to do it but if durability is a concern then I would put a lot of thought into how to isolate the tail pipe from the rest of the exhaust.