Do you know what's reused in your typical remanufactured engine? The bits that don't wear, like the block. That's pretty much it. There is no good reason to buy a new engine rather than a remanufactured one.
You should also consider whether or not you really need a remanufactured engine. A "seized engine" doesn't really tell us much, but the most common causes would not lead to the destruction of your block and heads. Most "seized" engines can be rebuilt. If you don't want to do that, get a short block, do a valve job on your existing heads, and put it all back.
I would not suggest a salvage yard engine. The only time it's really reasonable to use those are when you're able and willing to pull them apart, make sure the internals are all within spec and then reassemble with all new seals/bearings/etc. If things aren't within spec, you'll need to strip it to a bare block, send it off to the machine shop, and do a rebuild. In which case, you've just remanufactured the engine. Swapping in a salvage yard engine without doing this is foolhardy.