Rob,
Great to hear this vehicle has found a new home! I really like this type of vehicle, that's why a wrote a web page on the
Canadian Armoured Snowmobile back in 2002. The website is gone, luckily a copy was captured by the Internet Archive - see
http://web.archive.org/web/200910261...nowmobile.html
But you're not going to try to buy a V8 Caddilac engine in the UK, are you? I'd look around in Canada or south of the border, once you start your search I am sure you will find them quite easily on your side of the pond.
See
http://www.mapleleafup.net/forums/showthread.php?t=15 for some more background on this vehicle or search the forum for "Penguin"
Hanno