You should be ok with the “old’ 1969 Enfold, a friend took a 1972 Enfield back to the USA!!
If you can get an India Carnet, may be the customs will let you out!!
I found out from a Belgium journalist, who was doing a ride back home with out “paper work” so he could write his Sunday paper reports as he went!! He had to get a Nepalese registered bike, at a higher cost!! But as far as I know he made it home!! His name was Mark?
The customs on the India side of the border with Pakistan, I found very helpful. I had to change over carnets & I needed an extension, they did all this at no cost, but it took a day of talking & a day to the paper work!!
The down side! Their on the ball, they know all the rules!!
"Still there are people doing overland without carnet. Only one way to find out I guess....."
When I was last at that border crossing, I meet a French family, in a camper van, on Dutch plates! Who had made it all the way to the India border, but the customs would not let them in with out a Carnet!!
The customs people really had tried to help them & let them leave their van in the custom house safe parking!!
Why not go up & speak to them?
Ride Free, Ride Safe, Ride one more mile,
Rik & Changeling