Sounds like an expensive step backwards... I would think by the time you swapped in the 355, you could probably have your 5.3... Do a little searching and you could have a 5.3 crate for ~$5-600, with harness, ready to bolt in... I think with the crank spacer, your LT1 T56 would bolt right up.. fuel would be easy.. stock LS1 engine mounts should be easy to find. A little searching, and some elbow grease, and you can make the harness a standalone...
Of course everyone has their own ideas, but I think the 355 might end up be a bigger pain...