Thanks for the interest. I have thought it out very carefully. I will have the block sonic tested before boring but from checking through the water jacket holes the cylinder walls are consistantly .25" which will leave .18" after boring. I have read people are running 500hp blown engines with .10" wall thickness so I feel pretty safe. If the 560 rings are chrome they would work in a iron block.

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Tony H
W111 280SE 3.5 Coupe
Manual transmission

Past cars:
Porsche 914 2.0
'64 Jaguar XKE Roadster
'57 Oval Window VW
'71 Toyota Hilux Pickup Truck-Dad bought new
'73 Toyota Celica GT