Welcome!
LT4? That's the ZR1 motor, yes? Well, I think that cost and (lack of) availability is the main reason for not using it.
LT1's are great engines and they don't have a distributor per se. I wouldn't consider the Optispark to be a distributor really, but I suppose it functions in a similar manner. Some like 'em, some don't.
Anyway, I believe the LS1 block is aluminum (someone correct me if I'm wrong here) and their availability is getting better and better. I love that, because it makes LT1 motors get even cheaper...
The primary thing you would have to find out about the LT4, if you are planning to go that route, is where the mounts are in relation to the standard 350 block. If the attachment points are the same, then using the JTR method would be a snap. Of course, then headers would be the next question.
If you have a good amount of cash to do such a swap, it would be extremely cool and very unique. If you want your dollars to go further, and wish to do a minimal amount of fabrication, then a modified LT1 is a great way to go.
Good luck on your swap whatever you decide!
Davy