1. Hook up with the rsc-forums
custom hardware-section. There are lots of threads where people discribed how they built their shifter from a gamepad. Some really complex, some easier.
All in all, you will be likely to come up with your own design, inspired by other people's design, for example the picture you posted (that design looked good, with those clips inside the gates as connectors).
2. About the pedal: Once again, you can copy most of the design from other people over at the rsc-forums.
I have a MOMO Force, and a spare potenzometer from my FFB-shifter, so I'm in a similar situation like you. I think about turning the MOMO-pedals with the footrest pointing upwards and use the current break and gas as break and clutch. Then I'd place a third pedal made from the pot and place it right of the MOMO pedals as the new gas-pedal.
But I'd suggest you to open your wingman-pedals, remove all the throttle-pedal-stuff and saw the remainders in two between throttle and break. Then place the break-part left of the MOMOs and fix it with something in place. A wooden frame, glue, chewing gum, whatever.
Then plug the Wingman-pedal-remainder to your windman-steering wheel, plug the wingman to the usb-port and recalibrate the pedals. Then make LFS use the break-axis of the wingman as clutch. Voila, a clutch pedal.
My suggestion is to read about how other people's ideas turned out on the rsc-forums and then decide what will work out for you.
Vain