I think you could do this but even if you put lipstick on it, it's still a pig.
Why ruin an ever more rare 122? I have a running 240 diesel and it is getting along fine on biodiesel. A friend of mine has made a processor and I collect the oil for him. He drives an older 300sdl Mercedes. Any diesel engine will run as well on biodiesel as petrodiesel. I'm running B100 which is the pure stuff. It costs him ~ 60 cents/gallon to make. It is way less polluting than petro diesel and smells like french fries or fried fish, depeding on what it was used for. There is more oil available than a body can use so it is a very credible source of fuel.

I suggest that you look around for an older benz to convert to WVO or fuel w/biodiesel. The 123 chassis is the preferred model. The engines are very stout and take especially well to the WVO conversions. The increasingly rare 240 Volvo diesel is not as good a vehicle for this because the engines were somewhat fragile for a diesel and needed more maintainence. However there are a few good volvo diesels around but generally the owners won't part w/them.

Forget your Frankenvolvo scheme and put that money into making a biodiesel processor for your diesel benz. BTW, go to www.bobistheoilguy.com and check out the biodiesel section. The benz forum also has tons of biodiesel info on it.

cogito ergo zoom