From my research, in the USDM the
5161 is a 1.5 ton bottle jack, included with the Datsun 520/521/620. Several different top flanges were produced during the 5161 production period.
375161 is a 1.5 ton bottle jack, included with the Datsun 720. Also, this jack seems to have been included with the Patrol 1983 MQ series vehicles, not offered in the USDM.
The 5161 does not fit the USDM Patrol's jack mounting bracket. (I have not tested the 375161 to see if it fits the USDM Patrol's jack mounting bracket.)
Not jackin with Ya!
Keith