According to one website, the 6.6l (402 cubic inch...a 396 big block bored .030 inch over, either by the builder or by GM when a batch of 396 castings were discovered to have a core shift...they were sold variously as 396, 400 or 402) motor wouldn't pass emissions testing in the Scandinavian country in which the owner lived. That doesn't surprise me with a Donovan motor. If it was built like many of the other motors produced by Donovan Engineering, it would have been pretty radical and would probably not be real "clean." As a result it was replaced by a Chevy smallblock motor. That could be anything from a 265 to a 406, most likely a 350, possibly a 305.
I suppose the photo is the process of the motor swap.
RtR