Jakob,
westfolk and cranetruck are correct, first, when the accessory switch is on, you should at the very least hear the low air buzzer. Check the starter switch and connections behind it, although you only changed the clutch and shouldn't have messed with that stuff...I hope.
One thing, and it's a very long shot but it's worth a look see.
On the bellhousing bolts there was (or should have been) a ground strap under one of the bolts (on the upper right side when sitting under the truck looking at the flywheel). These motors are grounded in a few places, and that's how the starter current get's back to the battery. At least one of my block grounds are not connected (it was like that when I got the truck). It's a slim possibility that you may have similar "unhooked" grounds, and if you forgot to reconnect the bellhousing ground you may not have a good enough ground to allow the starter to get power flowing.
Like I said, it's a long shot, but if all else fails, take a set of jumper cables and ground the block to the frame or the negative battery terminal and see what happens.
just my
