Anyone here put a 354 in a Dart?

do you mean 354, as in early Hemi? I've seen a 440 BB in a 64 Dart, and they cut the crap out of the inner fenders for headers. Granted, yours is a wider Abody, and they did come with optional 383's and 440's, but even then they were a tight fit. It is a really nice looking car as is, and yes, the 354 would look outrageous, but I think it would be a really difficult swap, and the benefits don't outweigh the costs. An LA engine would be the easiest, then a Magnum, then 3rd Gen Hemi, if you want more go, and more wow factor. Maybe consider a turbo swap onto the /6. I think it's been done enough, that most of the pitfalls have been worked around and scienced out, now.