Mmmmm! I had viewed this, collection!
Could be a short stroke 350cc created by shortening the 450cc barrel and using a 250cc rod and various other internal mods to make it 'work'. However, because of the short stroke and high piston speeds, piston ring and bore wear can be high. Also, it has been "standing for 10 years or more". So, what condition are the bearings etc. in? An expensive collection of bits, £2K too much. Even with gratis transport across the 'pond'.
But then I'm a cheapskate!
My regards, Bill