The problem as I see it is the documentation that the rifle is 50 years old. I don't know how stringent HPD's requirements are on that for proof. In order to avoid that issue I could do the transfer through the 01 FFL, but as you said that entails the transfer fee and totally negates the purpose behind the C&R license.
I would love to see some legislation that added C&R firearms to HI registration exemption list. But then again I wish the whole thing went away, so if the gun control groups can use incrementalism, so can we! 
I would write a letter to the firearm company. It will take some time, but it might help with registration if HPD balks at whatever else you can find via Google. It might also be of interest to you or another collector if you sell it.
Send as much info as you can: model name/numbers, any graphics, engravings, etc., and vital statistics: barrel length, overall length, caliber, magazine capacity, finish, part numbers, .... Include pictures of all sides, close-ups of identifying characteristics, and any other images you think would be useful.
If the company gets enough information along with sharp, good quality photos, they may be able to issue you a letter stating year of manufacture among other interesting facts.
You never know. It's worth a shot. You might find it has a history you never knew about.

GL!