A 454 block with a 396 crank is a 427. Nothing crazy about that....the only problem is that you will have to add heavy metal to the crank to compensate for the extra weight of the larger 427 pistons. at 25 bucks an ounce plus the extra labor you might be better off getting a new crank.
If you have the complete 454 just build that one up. You will get better power and unless you are going to spin it up to above 6500 RPM regularly then there is no need to destroke it.