It's a pretty wide-ranging question. Is it more that you want to run a weird OS or that you want exotic looking hardware? Do you want to actually use it for more than a few hours each month?
In my university days, there was a 730 (or maybe it was a 750) in an electronics lab. It was a little half-rack thing, or maybe two half-racks. It wasn't even on a raised floor.
No, but this someone did take it into his head to scratch build a Honeywell 200 at home to prove that it was better than a 1401. That was almost fourteen years ago and I still have a way to go. Just don't try this at home yourself! Also as others have mentioned it isn't finding room for the CPU that's the issue but for the peripherals. That problem is still a long way off for me. At least I do now have the all important blinkenlights working although just getting the 35 pound heavy control panel flown over the pond from the USA made a hole in my project budget.
Some time ago I did correspond with someone in Germany who had a Honeywell tape drive at his home and I sent him some replacement vacuum switches that I happened to have to help restore it but I never heard whether he got it working. It's not the sort of thing I'd want to shift around my home though. I do still have reel motors with hubs and a couple of reels of tape, so could mock up something that at least looked like a drive to put next to the CPU with its genuine blinkenlights and core memory unit. I think that's preferable to a real tape drive and mock up CPU.
I agree, in the post regarding the 1401 it was more in the spirit of having an original (one could argue how much of one makes it original). I am however of the view to change slightly regarding how common such machines (not on its own the 1401) but as a wide collection computers that are in private hands (1301 ICL, Zebra that was found a few months ago in a German barn, the Bendix G-15 found again in a barn a number of months ago, 1401 in Germany that was purchased in 2009).
An ETA-10 lacks the STAR's massive instruction "everything but the kitchen sink" set. It was fun finding ways to use some of the more outré instruction variations. I wrote a line editor in the 1970s to do just that as a lark. It was still in use at ETA in 1984--someone replaced the no-longer-implemented instructions with software simulations.
Some time ago I was talking to the maintenance engineer at the National Museum of Computing at Bletchley Park here in the UK and he mentioned that our national Computer Conservation Society do require a specific percentage of the components in a machine to be originals for it to be regarded as a restored machine rather than a replica. I don't know what that percentage is but at least they don't argue about it.