I know a few people have done it, but how reliable can the engine be with a stroke that big? I know that the block design on the LS1 allows for the long stroke to easily be used, but what about the LT1?

 

The block and the rods must be clearanced, and you may need a small base cam.
Yes, it's been done. But general consensus is that the increased cost of parts/machine work over a 396 aren't really worth it for most people (I realize "worth it" is very subjective). You get to a point of diminishing returns as you try to increase displacement with these blocks.