Yep, make it legal. Heck, the Vaqueros came around long after the Ubertis and Great Westerns had been on the market. I had both of those back in the 70's which, I believe is before CAS/SASS. So, if Vaqueros are allowed, along with other non-replica replicas (Cimaron Thunderer comes to mind), then why not the Henry. My son has one, and it shoots wonderfully. Smooth action, and good for huntin', too!
Ride Easy,
Smokey Jim