http://www.ford-y-block.com/Block%20identification.htm256 cid was in Mercury line up and was called "V-161" Advertised hp was 161 at 4400 rpm and torque was 238 pounds-feet at 2200 to 2800 rpm. Compression ratio was 7.5:1. That is what my "55 years of Mercury"-book tells me.
And yes, my "Standard catalog of Ford 1903-1990" says this for the 1954 year. Law enforcement V-8: 256 cid, 160 hp at 4400 rpm, 7.5:1 compression and one Holley four barrel. Serial number code "P".
So, it was 