The more heat you can keep in the exhaust before the turbo the more efficient it will be. You don't want to have a long distance between turbo and exhaust ports as this is a good way to loose heat.
If all you want is looks you may not care about all that, and if that's the case just plop an extra turbo on the other side for looks, no need to make it functional...
If you want twin turbos, one on each side, a V type engine would be simplest, like this V6 in an f350:
I had considered a twin setup on my 4-53T, as I can get two 2 cylinder manifolds and they bolt on, but for now I just don't think it's worth the effort. I think the Detroit would be OK pairing cylinders 1-2 and 3-4, as they fire every time the pistons get to the top?
Grigg