If you really can't stand the wait, Pedersoil produces a side by side rifle in .45/70 caliber.
About $1350.00 retail and very, very nice.
The Baikal is supposed to use a jackscrew arrangement to regulate both barrels to one sight.
Teswt fire and screw, test fire and screw until you get both barrels converging at whatever distance you choose.
Pedersoli just soldered the barrels together after a rough cross pattern line up and uses two different rear sights.
One for each barrel.
Sounds hincky but in use two rear sights allow the shooter to regulate one barrel to point of impact-point of aim at, say, 50 meters and regulate the other barrel to impact point of aim-point of impact at, say, 100 meters.
Remember, no side by side will ever be judges as a target gun.
They are close range meat eater killers and the previous poster is correct that neither gun will stand heavy pressure loads like a custom British double but the Pedersoli uses a chopper lump type barrel arrangement and a pretty solid, double locking lug.
I don't know exactly how the Baikal is put together unless they are building them like their over unders and that will be solid, fluid steel barrels, and a Greener type crossbolt lock-up. HTH