Is there any way to simply change the file version of a nif from 8.243.82.50 to 4.0.0.2 using Nifskope? Morrowind crashes when I use a model with the file version 8.243.82.50 so I'm having to change it back somehow.

Nope.

Dang, oh well. Thanks anyways.

Actually that depends on a model, e.g. in case you are able to open it in NifScope and the nif contains only not-skinned meshes you can try to export them as obj and import back in an empty MW nif. I have never seen 8.243.82.50 nif format, is that what you see in the nif header?

Er, I thought you could do this?
The NIF version is just a tag on the root, isn't it? I was pretty sure you could edit it like a block property in NifSkope.
Edit: Although it's just a technical change, a simple hack of the version-string. It could break things, or it could trick it into working.

As for the 8 version... I've seen that, but I can't say where. Morrowind supports 4.something and a few dozen minor variations in that area (I have a few pages of all the minor varieties it supports).
Be aware though that Bethesda heavily modified the NIF format: the official NetImmerse Gamebryo tools (for versions 1.3 and 2.0 of the engine) aren't capable of importing or viewing Morrowind/Oblivion/FO3 files or the other way around.

This tag is not a problem: nodes format is different (e.g. compare NiTriShape node form OB with the one from MW). This results in different binary and game CTD at the end. NifSope does not allow to copy/paste branches from different formats. Indeed, nifs are not down-compatible, up-compatibility works also not always. As far as I know engine package contains “up”-converters. Modifications introduced by Bethesda is an additional obstacle.

If the mesh isn't skinned (has bones), you can do it with blender. Just import it, and then export it with the right exporter. You can even get some animations to transfer this way.

However, the vast majority of people want to transfer armor or clothing, and that requires more effort.