14,100 had wrinkles 11/69.

  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. 

 Thanks for the thread, I enjoyed it and am always on the lookout for new to me information. I've had some luck with google photos and moving them using a thread on the sohc4.net open forum stickies.

 5511 has one dimple above the bowl right side, 14,100 has one on the right side, approx. 10xxx one right side, 38,xxx two left side. There was a discussion on facebook and I checked.

 I've often thought it would have been interesting to have witnessed the building momentum of the 750 factory, from a few bikes, to a few a week, to a few a day, then dozens, then hundreds,  etc, etc,

 Good question, I have one bike that is for sure original, sandcast 5511, the 14,100 diecast has a different swingarm although it was from an earlier frame and my late K0 I think is original. If I get to the shop and can get between the bikes I'll try to compare them.

 Good to know, my 14,100 has a semi rounded rear wheel available to it. 5511 got it's original rolled rim wheel back from the drag bike it was loaned to.