Kuryakyn Passenger Floorboards
I had good luck installing passenger floorboards using Kuryakyn products and it wasn't all that complicated so I thought others might be interested.
I went with Kuryakyn 4357 black floorboards because I liked the size, look and adjustment possibilities. However, it seems like ANY Kuryakyn product that mounts onto a spline adapter should work.
Remove the pegs by pulling the clip off the end of the mounting pin and sliding it out. Take care to catch the little steel ball and spring that are in there. I didn't know they were had to search for an itty bitty piece that escaped. The pieces are important if you ever intend to re-install the pegs.
Kuryakyn will tell you they don't make a spline adapter for the VN750 and technically that is true. However, the Kuryakyn 8813 adapters works very well with a bit of work. It came closest to fitting into the space between the mounting brackets holes. The difference I shimmed up using flat washers. Perhaps other adapters would work as well but the ones I looked at were narrower and would need more shimming.
The main issue is that the mounting bracket hole hole is a 12 mm (1/2" almost) and the spline adapter hole is 8 mm (5/16"). Obviously if it was mounted that way the adapter and floorboard would just wobble around. My first thought was to just re-drill the adapter hole to match the mounting bracket hole. The problem with that is you couldn't use the set screws that come with the 8813 adapter to fix it in place.
A solution was to insert a vinyl spacer into the mounting bracket hole. I bought a 1/2" OD x 1/4" ID x 1" long vinyl spacer from the hardware store. This eventually gets cut into four 1/4" long pieces. Note: There may be a source for a 12mm x 8mm x 1" spacer or a 1/2" x 5/16" x 1" spacer that would make much of the rest of this pointless. However, I couldn't find that at our hardware store. So...
Re-drill the ID of the spacer using a 5/16" bit. A different adapter might need a different sized hole. I wrapped a bit of sandpaper around the spacer and held it with pliers so I could drill out the hole. After drilling the hole, leave the bit in the hole, lay some sandpaper (I had 120 grit hand and it worked well) on a flat surface and use the drill to sand the OD of the insert down until it just fits. The inserts should not slide in loosely. Ideally, they will press in when you tighten the nut on the mounting bolt. When you have it the right size, cut the spacer into four 1/4" long pieces. I slid it over a 5/16" wood dowel (to have a good support of the piece and to keep my fingers out of the way) and used a coping saw. A utility knife would work, too, though with a bit more effort.
Install using a 5/16" x 1 3/4" hex bolt, washers, inserts and lock nut. Order goes like this: Bolt, washer, insert, mounting hole, shim washer, spline adapter, shim washer, mounting hole, insert, washer, lock nut. A third hand would sure be useful sometimes! Let the bolt and nut press the inserts into place as you tighten. Make the nut snug but don't over tighten. Those mounting bracket holes look like they could snap off fairly easily under pressure. Then use the set screws that come with the the spline adapter to fix it in place as you like. Finally mount the floorboards onto the adapter using the screws supplied. The 4357s have five options so I was about to adjust it to fit my wife's preferences.
My wife LOVES how much more comfortable the floorboards are. I picked the floorboards up on sale for $120 and the spine adapters were $25. I spent a couple of dollars on bolts, nuts, washers and the spacer.
If I can figure out how to do pics, I will post some. All in all this was a great project that didn't require me to cut or drill anything on the bike itself. I'd recommend it as a good way to go for Kuryakyn floorboards.