"Maybe some other parts" is a bit vague don't you think?
I would only do it if I had a lot of experience with projects like that, or if I needed an extra Twilight Zone for parts. Both are not the case

i would buy it if it were cheap and only had a few missing bits n pieces..u can buy the clock and most parts, given the large proiduction run.also, there are plenty of professional people in the industry who could give it the once over and give you a quote to finish it up.sometimes a project can be rewarding if u get the right people involved, and lets face it, EVERYONE loves a twilight zone...i say buy it.
p.s- conversion back to usa power is very very simple.very inexpensive.if thats the hardest part, as any pinball tech will tell you, its a easy easy one to do up.
p.s- marcospecialties and bay area amusements have lots parts, any pinball tech will have his connections as well.

You can buy the clock anywhere. It really depends on the shape of the pinball. Playfield, cabinet, boards, and should know what else is missing

You need everything in the "zone". I think that's not a very good deal because the parts don't feel right if you buy them seperatly. Buy another cheap machine with all of the parts.