I don’t know about the 261 but I would think the aluminum ones are not stock .I thought they were all cast
That's what I thought Kevin. I have 3 older 216's 2 later 235's and 1 '54 261 and they all have the cast "steel" supports. About 6 months back there was a seller on Ebay with a complete OEM assembly of shafts, rockers, springs and aluminum supports for a 1963 year model, trouble was the price was close to $900.00. I'll keep researching and see what comes in.
Bud