Hi, Just measured the the pin on my Rd400 and it is 20 mms long including the domed head. Comparing it to the stand on my 31K LC, the 400 is a lot chunkier steel rod, 8mms in diameter so don't think the LC peg would be suitable. I assume the 400 stand is a heavier item because it's a heavier bike and has a stronger spring. I would have thought it would be easy to turn a peg from steel bar if you have a centre lathe, or ask a local engineering firm to do it.
Hi, Have measured the pin on the 400 with a vernier gauge and it is actually 10 mms in diameter. The domed head is 16mms across. The pin on the LC side stand is as you stated is 8mms diameter. Hope this helps?