Question re:Old & New Huntsmans rifles

[OldSchoolRanger]

 While browsing thru the forum, I discover posts regarding a .45cal Huntsman, made by H&R. I spent a lot of time on line today trying to find out the difference between the old H&R Huntsman (.45 cal - non FFL required, carbine type stock), with "push in/out" breech plug & #11 primer, and the later NEF/HR Huntsmans model (.50 cal - FFL required, 209 primer). And search as I might, I couldn't find anything other than how some posters were having problems with the .45 cal Huntsman, serial #'s prefix "AL" series.
What I was curious to know was:
1-Why were the older H&R Huntsman (AL series prefixes) guns considered non FFL guns, while the newer Huntsman guns were considered FFL guns. Is this because of the same reason as the Sidekick being considered a non FFL gun (different size frame)?
2-If barrels from the newer production Huntsmans models interchange with the older Huntsmans (Serial prefix starting with AL).
3-If so, would it be safe to fire the older frames with the newer .50cal BP barrels?
4-If it was possible to replace the "push in" breech plug with the screw in type. I know some work would need to be done, but could it? How would it be done?
5-Would H&R 1871, do repairs on these old guns.
6-Do the ramrods H&R 1871, currently sell for the .50cal Huntsman, fit the .45cal Huntsman? I believe Bubba posted that NEF sold replacement ram rods for $7 and change, along with the website. I tried it, but the site seems to be "down".
I hope I didn't rehash some old topics. I tried my best to look up the answers, on previous posts.
Hopefully quiickdtoo or Busta, can shed some light on these questions.

[PHATINJUN]

The reason for the FFL is the .50 Huntsman can have and the factory will fit other bbl's to the frame. The older Huntsmans were made by H&R and are designated BP only. They were not even acknowleged by HR1871NEF and no one will work on them they are basiclly the gun that brought H&R down all of the old Huntsman frames have fat firing pins. Even though some bbls can be fit to them either by modification or other means. They are still considered non ffl weather thats a snafu by BATF or what I do not know. I will not address the plug alteration.Not all were push in I have both threaded and non threaded and am using a alternate plug with Blackhorn powder in one of my.45's. The bbl's are mostly 28" so the new H&R ram rods may not be long enough I will check that out with mine and get back to you on that. I have several of the old Huntsmans .I hope this helps you. Kurt

Also ML do not have the same pressure effects on the frame as centerfire bbl's most of the pressure is contained in the bbl itself. So if a .50 can be fitted it should be alright . I am shooting Blackhorn @ a pretty stiff rate out of one of my .45's maybe not a 150gr magnum load but very stiff  and mostly anything over 100gr in the .50Huntsman's is a waste of money.

[OldSchoolRanger]

PHATINJUN,
Thanks, you answered all my questions, and then some. It's nice to have people that have all that knowledge on this board. I didn't know that there were 70's era Huntsmans until just recently.