You might want to PM Rat Patrol here. He just ordered a 6.1, including teh MSD stuff and I think there was a question regarding the 5.7 and 6.1 ingnitions. I don't think he's going your ETs, but it might be worth it. He's also familiar with pricing as it had to go to Australia...
Also you could talk to member swifter as he has a 5.7 that was stock stroke untill last year in which he has it stroked now, but my guess is he would be full of good info on going to a carbed 5.7.
