Well, the bearings are two Totally different widths so Creative offset grinding will be required not only to increase stroke but also make the narrow/late 970 bearings ride properly...which is what I hypothesized looking @ the two cranks.
So, yes..you Could use a stock 117 crank but the guy grinding it is going to have to be Damn Good.
jono
I hear that for the first time Jono. I know for a fact that the AMG 6L crank has a 117..... part Number (from the 560 engine) and that only the counterweights are diameter reduced - not more not less.
I know that the bearing sized are reduced on later M119 engines, but when you take a closed deck 974 block it should be no issue. Also having written with Bernard who builds these engines, he never said anything with the bearings. He said M117 560 crank, counterweights reduced and thats it.
A 560crank in good condition you can get for 500€ off ebay or in the W126 Forums sometimes.
The pricetag for the counterweight reducing + crank balancing was ~500€ at a engine shop i once quoted price from them for IIRC
Boring, Honing and silica polishing was 490€ at the same shop.
Pistons (Woessner) with special Alusil coating and rings are 300€/piece
Rods you take the 5L ones.
Headgaskets custom made at Elring were 200ish €/piece if you take a set of 3 from each side
So for the core "material" alone (if you could sell the other 4 headgaskets) you are more in the 5000€ range. Sure, with "little" stuff like for instance 32 new "tappets", chain, tensioner, replace all ignition stuff and all sensors, camshaft regrind, intake manifold/heads portmatched, all other gaskets, etc you get up to the 10.000€ mark (When you do it all alone - no labour costs).
The question is still, if its worth it...