10 inch front drum assemblies wanted

If the disc kit is based on the late model single piston calipers, your track will increase. If you stay with the early factory Kelsey Hayes four piston discs, it should stay the same; and also allow you to keep your 4" bolt circle wheels. The later model discs will change your bolt circle to 4 1/2" and you'd need different wheels anyway. Beware of the kits that offer late model discs redrilled to a 4" bolt circle, the hubs aren't always turned down to the 4" bolt circle's smaller center register- it may or may not be an issue with your particular wheels if they're aftermarket, it will be if they're factory wheels.
The 10" drums use the same lower control arm as your 9" drums (and the discs do too, for that matter), so you'll be able to keep your sway bar. Late discs need the calipers to be rear hung for sway bar clearance, early discs aren't an issue.