How interchangeable are the Gutrippaz and Man-Skewer Boltboyz kits?

[Condottiere]

I got some Boltboyz, but looking at the sprue, there aren't that many head variations. How much work would it take to fit the heads from the Gutrippaz kit - the multi-part one, not the ones from the Dominion box? How about the bodies? It looks like Boltboyz only have 3 poses, so are Gutrippaz the same size for conversion work? I know it'll take a bit of work, but wondering if it's possible. I wanted to convert a unit for use as mercenaries in WFB 5th and 6th Edition that's different from Ruglud's - I've got around 60 of them in my pile of shame. The Boltboyz large crossbows with bayonets look like spears or pikes.