Yea, I'm pretty sure none of mine have the bayonet lug, so we're good there.
This whole "non-NFA/other" thing still baffles the heck out of me, but I like it. haha. You measure from threaded part of barrel to end of buffer tube for OAL, correct?
If any of them have a bayonet lug, that has to go too.
The key features are the VFG and a minimum overall length of 26". The barrel length is not a problem. There are longer than milspec receiver extensions that will make an AR with a shorter barrel legal as a non-NFA Other.