It sounds as if you should get as many detailed pictures and descriptions as possible from that guy, while he still has the mowers. You may not get many other opportunities to make that kind of comparisons.
When it first became evident that his mower had the same small anti-scalping wheels as yours, together with fat tyres, it began to look as if both yours and his were built that way (unless some weird conspiracy of HD8 owners had taken place in the distant past). One of the rarest but most valuable things an equipment restorer can get, is contact with someone who has an identical machine in good condition.
