I've got a 92 swing arm and shock that will fit on your bike for sale. I just got a hold of a 95 1100 arm for my bike. When do you want to do this conversion? My swing arm may go on soon or in the winter. I was going to put the stuff on ebay starting at $100.
Here's what I know. I've put a '94 1100 'camelhump' swingarm on my '86 750 project frame. I've seen several other such equipped bikes. You won't be able to use your '86 shock with the linkage from the newer swingarms. it's a innie/outie or a male/female type thing. The shock on the 86 is innie-upper and outie-lower while the '94 shock is the same on both ends. As far as changing geometry, I don't think it's a problem as I'm not trying to keep up with Matt Mladin.