Boeing 737 seat mounting bolts - size?

[FAA152]

Hello, I have a friend who is building a home 737 simulator and he has a bit of cockpit floor with the seats supplied separately. He tells me the seat mounting bolts (not supplied) go through the cockpit floor into captive nuts. I have asked him about the 737 year, type and seat manufacturer but he says the bolts were all the same.
Does anyone have any idea what the bolt size is?
Thank you for looking at my exciting post.

[yotty]

Each seat has 4 tracks which are bolted to the floor. Then the seat runners (fitted to the underside of the seats) are allowed to travel along the tracks and have captive bolts at each end of one of the tracks to prevent the seat coming of the end of the tracks. I'll check the IPC next time I'm back on shift.