Trapdoor long barrel/carbine stock?

[berettaprofessor]

I came across a Springfield Trapdoor 45-70 rifle with good metal and what appears to be the long barrel (approx 32 inches) in a carbine stock. The carbine stock has the appropriate cartouche and does not appear to have been just the long stock shortened by Bubba, but appears to be an actual carbine length stock. Serial number in the 238xxx range. Two questions:

a) Is this a post-factory modification or were long barreled Springfields produced on carbine stocks at some point?

b) Any idea of rough value, given that not much original bluing was present but the rifle appeared to be in working order.

Thanks.