Unfortunately I already have my sights locked on a rare Topre that pops up occasionally here and there on Japanese Auction sites or I might take you up on the offer.
The difference between the 86U and the 87U basically are that the 87U has 2 windows keys while the 86U only has 1. This is more important than you think because it affects the size of the spacebar, all Topre keysets only include spacebars that fit the 87U version, you won't be able to replace the 86U's spacebar except by cannablizing one from another 86U or finding someone willing to sell theirs (It's the same deal with 103U and 104U). Of course if your not planning on buying any topre keysets the point is moot and there is not real difference between the 86U and 87U.