DON'T PUT A .45 LC IN A .410 CHAMBER!!!!!!! Check out the Rossi/Taurus Circuit Judge which is specifically chambered for both. Check it out on Cheaperthandirt.com under the shotgun tap. Its a revolving shotgun.
As far as a .410 having enough energy to drop a deer, thats more about shot placement than anything isn't it? I have a co-worker who's father gets varmint tags for deer (Lucky SOB can shoot them with whatever he wants because its technically not hunting) and has dropped a few deer with a .410. He said the were about 25 yards away, but it dropped them just like a 12 gauge. The experience is limited though because he usually uses a .30-06. Again, because it's not hunting, he's not bound by the whole "no rifle/caliber restriction" hunting laws.
========And yes, he did run that by the conservation officer.===========