Maff, going to be a wild ride for sure. I'm trying to figure out a way to transplant the LT1 from the wife's Camaro into the Miata but I suspect she might notice.
What you do is, as Eric (foolish) suggested the other day, and do the FULL swap. You put the LT1 in the Miata, and the Miata drivetrain in the Camaro. She'll never know the difference! (rlaugh)
After I got the battery for the Miata and installed it, tried starting her but she didn't want to fire. Gave her some gas and she fired, but sounded like she was running on fewer than 4 cylinders. Pulled the plugs and it looked like only firing on one cylinder. After some downtime while I cogitated, I yanked everything down again to see where I had made a mistake. Checked to make sure I hadn't screwed up on the timing belt or left an electrical connector disconnected but everything checked out. After it was all back together fired her up again with the same result. After some more downtime to beat myself up, I bought a set of feeler gauges that went down to 0.0015 (my other set only went to 0.005) and checked the valve lash. Apparently I am an idiot because all but one of the intake lash clearances were very tight, and the exhaust clearances weren't a whole lot better. I am not sure of the cause of this, my caliper did malfunction but I don't think to the degree that would have resulted in this. Anyway, with my new digital caliper and feeler gauge I checked everything and figured out what I would need for new shims to fix it. Got those on order and now just waiting on them to show up so I can see if this will correct the problem.
Tight bucket clearances should increase wear, but they shouldn't keep it from running properly...unless they were at 0, holding the valve open so it couldn't make compression. In which case...yeesh.