Small block IS technically described as 400 c.i. or less!
Our Viper engines "were" originally defined as a small block since it came from a 360 engine. That was fun while it lasted!
OK, lets really muddy the waters. I didn't want to get into it, but yes you CAN run/install a BB motor in the new "larger footwell" frames. But, it depends on the tranny. Can you still use a T-5? YUP, you sure can. In other words, slap that 460 in there with a TKO-R-Z-OD, but be prepared to use a hydraulic clutch mechanism.
I love these cars!
DV