Midway through the 1961 model year, Valiants (and the new Dodge Lancer) could be ordered with the 225 as an option to the 170. These were still all cast iron engines. A few months later, the aluminum 225 was released as the predominant optional engine (a few iron 225s were also used) for Valiants and Lancers. It is likely that a few aluminum 225s were also installed in larger cars. There were a couple of engineering-prototype aluminum 170s, but none were installed in production cars. The prototype aluminum block 170s were made using the sand casting process. The aluminum Slant Six block was series-produced in the RG (raised or tall block) 225 configuration using a die cast process. This block configuration can be used with 225 crank/rods and with 198 crank/rods. Of course, the 198 was still years away (1970-74) when the aluminum engines were produced. I mention that the 198 crank and rods are for use in an RG block specifically because so many sources screw this up and call the 198 an LG engine (Low block, like a 170, with the lower block deck height). In summary, the aluminum 225 block will accept any 198 or 225 forged crankshaft (not the post-'76 cast cranks). Of course, the appropriate rods / pistons must be used with whatever crank is installed.
