My 5511 takes 46mm or 450 fork seals. 14100, built in 11/69 got the ones that didn't fit the Sandcast forks.
I went out and checked, both of my bikes have the non tapered tops. I have two more sets of lowers not on bikes, one tapered, one not. On those two sets only the brake side has the extra rib and it is on the tapered and non tapered. my 38,000 era 6/70 bike has the non tapered tops. It's hard to tell about the rib when the brakes are on. Both my K1 and early K2 front ends have the tapered tops.
None of mine have the slight taper. They are either the square shape or the fat taper.
For the record I'm unsure what forks were swapped at this time. I'm only positive about my Sandcast 5511, I have 4 K0 now and all except the 43,000 have the early tops that match my sandcast. I believe there was a change at around 39,120 in the K0's but the parts fische on partzilla incorrectly lists 46mm seals for all of them.