50,000 aluminum slantys were made....
Between 1961 and 1963, Chrysler produced more than 50,000 Slant 6 engines using an advanced die-cast aluminum block. Manufactured only in the raised-deck 225 CID version, this piece proved to be somewhat more trouble-prone than the standard iron block, with cast-in-place ferrous cylinder liners that tended to separate from the aluminium block casting. A special head gasket was also required.
Some of these aluminum blocks also included provisions for hydraulic valve lifters, though they were not so equipped. Sort of an anachronism in this regard, the Slant Six did not adopt hydraulic valve lifters until 1981. All previous versions employed old-fashioned solid lifters that required periodic adjustment.