Since 90% of Valiant's were /6's, just keep in mind the cost of the misc parts to convert to a small block. Not to mention you'll need a V8 904 trans also.
As far as the early 90's 360, it will most likely have a roller cam in it. While that's a good thing, the cam replacement, if you choose to stay roller, can be a little pricey......like $400ish just for the cam.