It's my understanding that stroking a 4.6 to 4.9-5L brings the pistons partially out of the cylinders at the bottom of the stroke which over time usually leads to accelerated wear. If you want that kind of displacement and are buying a block anyway then you are much better going with the 5.0L big bore block.
MMR sells the big bore block and can even build you a ready to go short or long block with one. Not cheap but they have a good reputation and they warrantee their work.
I personally have a Teksid block sitting in my garage that I was planning on building myself but am now thinking about just sending to them to have it built with one of their forged rotating assemblies. They have the experience to know what clearances work best for different engine setups.
