As far as I know the only 45-70 DR availible it the Biaikial/Spartan.

Whilst some have had some sucess getting them to shoot, I think the most charitable would describe them as rough.

Personaly I would go for an entry level 9.3x74, my reasons are these:

It will be of more satisifying quality and fit.

The caliber is suitible for everything in N America and will do everything in Africa up to and including Buff if you wish.

It will keep it value better.

Heads are plentiful.

Brass is cheep.

Regards