Yeah Tim--I have a Classic 38-55 with a 45-70 barrel too--the 45 colt with a 20" tube will be a sweet setup--I've had the Classic(same as BC) wood on my 44mag and I really like it. The 45 colt will certainly not suffer for having 2" less barrel than the standard Handi.
Quick, do you know if the factory will be supplying the rifle with the same sights they put on the BC?