Russell,
I am building the Zero kit. I went down the donor vehicle route as part of the fun stripping, cleaning and painting. 10 years in the planning 4 weeks into the build, you won't find a better forum or guys for advice and free information. As already stated don't under estimate the hidden costs of buying odds and sods.
I am going to be the odd one out because my donor came with a old crossflow so in the tradition of locosts that's what I am going to use - well at least for the IVA. Then the fun starts with all the modofications you can do......
Its great fun and a fantastic experience - take the plunge.
Regards
Mark
PS haven't decide how to display my build photos yet!