Thank you, TOH, for instilling confidence in going ahead with replacing thin wall steel with thick wall cast iron sleeves.
Just received the thick wall sleeves today from North Carolina.
Good to know that the block configuration did not change from 48 to 52 or maybe even as far back as 39 to 52.
There is a post on this forum in Jan 27,2003
stating,"cast iron offers a porous surface which
holds oil and steel does not."
Therefore cast iron offers better lubrication than steel and as a result less friction, less surface temperature, less heat generation
and more thermal efficiency.
Going to gray cast iron sleeves is defininely an upgrade over steel sleeves.