My shimano R107 shoes will take a two bolt SPD cleat, but again, they are a road shoe.
The key issue is that road cleats are too soft, any amount of walking on mixed surfaces will knacker them. My driveway is about 40ft long and gravel, you would be amazed what walking down it in road cleats does to them.
Just google shimano SH-SM85 ebay and you will find them.
As a response on you last reply. Walking in my situation will be bare minimum. I don’t want to do technical single track rides. Just some sand/mud trails. The technical stuff I encounter are somee tree roots…
Those seem designed to convert a 3-bolt road shoe to use the 2-bolt SPD cleat, not the other way around.
This does not include any way to mount the 3-bolt cleat in the way we want to in this thread.
You can do it the other way around. Bolt on the 2 mount system first and the 3 bolt system on top
It will require some additional nuts that fit under the 3-bolt location, that are not included in the kit. Not impossible to handle, but necessary parts beyond the stock kit.
Okay Obvious Question: Whhhhhhyyyyyyyyyyy???..
If you bolt a road cleat to a mountain shoe you have lost the ability to walk in them effectively completely negating any benefit to using a mountain shoe in the first place. Either run a mountain shoe with a mountain pedal or a road shoe with a road pedal.
I’m not following any reason to do this. I get the power meter part of the equation with the pedals but. Just pick up a 300-400 a few year old quarq s900 or buy a used stages for the left side arm of that bike. Way better option than damaging your road pedals, jacking up your road shoes, or totally bodging a set of mountain shoes into an abomination.
And that’s my 2 cents. 
For clarity, I had planned to remove the shoe cleats around the pedal cleat for clearance, and leave all the remaining mid/toe/heal parts of the shoe cleats. Idea being to make a more “flat” setup with a MTB shoe base and a road compatible setup.
Some things just shouldn’t be done. 
You could probably get on GCN’s Hacks / Bodges of the week with this one if you pull it off.
Well, that would be my 2nd time on there 
I don’t think this is a good idea. For gravel riding, you can surely get away with road-style pedals, but once you get into single track, you are just asking for trouble. If you want light MTB pedals, have a look at Crankbrothers’s Eggbeaters. I currently even run them on my road bike (because I didn’t want to spend money on a second pair of shoes and new pedals when I bought my first road bike last year).
I live in the Netherlands. So single-track rides aren’t technical. I don’t expect I ever need to unclip. So I can take my chances. When I ride gravel I can choose depending the weather if I go for road bike shoes or mountainbike.
When I go abroad then it will be another story.
A point that I’m not sure folk have considered is that road style cleats don’t work when the get grit or mud in them. Even unclipping to open a gate on a wet gravel road can cause problems if the cleats get clogged.
What about mud and dirt? Once you step into the dirt, you may no longer be able to clip in with road style pedals. MTB clipless pedals are made to shed dirt whereas road pedals are not. (The only exception I am aware of is a cyclocross-specific version of the Speedplays that have a cross rather than a lollipop shape.)
If I were you, I’d either stick to road shoes, power pedals and take your chances (which is cheaper) or, if you decide to spend the money on new MTB-style shoes, just add a little more for MTB-style pedals. I reckon for light gravel excursions, road shoes and road pedals are fine.
Glue a used MTB tyre to the bottom of your road shoes 
I considered that, and would try it if I already had a junk pair to use. As it stands, I have the opposite situation with an old set of MTB.
Either way may satisfy the design goal here.
On dirt and mud, I already acknowledged that potential pedal and cleat issue above. I don’t ride on wet roads (fair weather rider as mentioned).
Besides, I’ve already dealt with the dirt/mud cleat issue on occasion even with road riding. I’ve had to fix flats in ditches and side roads where the dirt is muddy and got on the cleats. Just a bit of cleaning with a stick and good to go.
I’m not planning to make a MTB-like messy use from my idea. It’s just a crazy option (again, already stated in my first comment, so I get it… not the smartest idea… I know… consider that horse dead…) that I am considering for a very particular use case (again, dry gravel with minimal off-bike use).
Dito for me
My use case is:
Have existing mountain bike shoes, Time Sierra.
Wish to mount iclic 3 hole road cleats on these shoes to use with road pedals on road rides.
Why? Because these mountain bike shoes fit me better than any road shoes.
The less stack height n any adapter, the better.
Picture of sole of Time Sierra shoes http://sscycleworks.com/images/shoes/Time-Sierra-ATB/time-sierra-42-0.jpg
