I've just had what I consider to be a rock solid confirmation of the requirements for SVA. I have just spoken to Mark Vickers ,who is the chief SVA technical officer for VOSA. He has confirmed that as soon as you cut into the chassis of your donor it is 'no longer' the original vehicle. It then becomes an entirely new vehicle that WILL require SVA'ing as an amature built vehicle. You need build photographs to prove that you built the vehicle yourself, details of the donor etc.
As it becomes a new vehicle you will get a new identity, new log book and if you can prove the age of the parts (ie the donor) then you will get an age related plate, other wise you'll get a Q.
Therefore, all LandRangers, Dakars, Hybrids, Bob Tail Rangies and any other vehicles where you have to remove part of the original chassis as part of the build, WILL have to have an SVA.
Obviously if you are doing a repair and replacing something like for like then thats fine, it keeps its identity.
Sorry for the bad news but I thought I would pass it on.
Andy