There's quite a lot to that, Look up www.parktool.com for instructions.
They fit the forks perfectly, but they do not fit on the back. You need certain size washers for it to be able to fit.
no they don't you need a shim to make them fit the forks
The downhill forks will fit on a normal mountain bike with a little fabrication.
Any 1 1/8 forks that are threadless
yes, scs is meant for thread less forks.
YEs
If it is threaded then yes it should fit.
yes but do not tighten t much becouse forks will snap
Any 20inch forks will fit.
Yes
Yes, 81 custom pegs will fit grit threaded forks. The 81 custom pegs will actually fit most of the current models of scooters and are easy to install yourself.
yes they will if you have a district headset