I replaced the temp guage and sender on my 93 NAS 110 with a new VDO 'Vision' series about two weeks ago. The sender I used is a M16x1.5 thread. The sender went on smoothly with no problems, and no leaks. The sender did not come with a 'washer' so I used the original from the OEM LR sender I was replacing.
I purchased the guage and sender form 'eguages.com'. The part numbers are:
#310-105 VDO Vision guage (250 degree)
#323-417 sender 250 degree m16x1.5
I hope this helps.