A 396-427 crank in a 454 block is a drop -in, you'll have no problems doing the swap, you'll have to use a neutral balance flywheel/flexplate and balancer since the 454 is externally balanced.
I also have a 454 and wanted to make a 427 out of it but got convinced not to do it because the shorter stroke would lower torque output, and torque is a good thing to have!
I'd like to build a 427 though, high revs are also fun
Martín