The Baikal doubles have been available in Australia for at least the last 12 months. Pretty bloody ugly - but cheap. This dealer has them listed in 223 Rem, 308 Win and 30-06 for $895 Aussie dollars (approx $650 US). I have never seen a reference to a 45-70 Baikal over here. I dont know that converting a 30 cal Baikal to a 450 would be worth the effort unless you did all the work yourself as a long term project.

Fergus