V8 parts are around in europe - more than you would think. I honestly don't know what I would do. It depends on what you intend to do with the car. If you want to keep it stock it will be harder to find another block. If a conversion to a later non stock motor is feasible, then a French or German motor could be swapped in or a later 24 stud USA 59A type motor.
Depending on the current bore size, it might be possible to bore to an oversize and get into clean non scored metal. If the scores are too deep, then sleeves may be called for.
I'll probably bring down the wrath of most people, but there is another approach. The engine runs, but knocks. You could just pull the pistons, carefully inspect the pins, pistons and little end bushings, and as long as the only problem is that two of the circlips have come dislodged or were never fitted in the first place, you could just replace all 16 circlips as a precaution, put it back together and continue to run it. Ok, two of the cylinders will not be at 100%, but 6 will, and the two bad ones will be helping a bit. It would probably continue to run for a long time. During that time you could be sourcing another motor or all the parts you would need to do the job sometime down the line when it suits you.
It depends on you, your situation and your attitude.
I'm not saying I would necessarily do as I described above, I'm just laying it down as one end of the spectrum of options available to you.
Mart.