Then I was thinking, there are different sized batteries for the Model 3, so maybe one is smaller, but this is and isn't the case. Tesla uses the same case for the battery pack, but uses different internal modules. For the standard range, the modules have been shorter, and they have been the same length, but inside the modules there will be rows of missing batteries, and they have been entirely different chemistry/module construction like when they started using CATL's LFP batteries. The LFP batteries are ideal for low cost, low/no fire risk, and high cycle life and performance, even if the battery density is not as high as lithium-ion on these units. Seems like the CATL batteries might be able to be removed in series, but this seems harder than that finding a short battery module.
Seems like this battery pack could be cut down by 12'' and welded back together along with the center of the car, which would make the wheelbase the same as the 86. Oh yes, it is a lot of work, but it seems like someone could do a wide body conversion and maybe do AWD or just RWD, depending on the donor car and swapping battery packs.
Tesla is starting to make the battery packs structural, meaning the packs are not filled with modules that float in a case, but are sealed in the case, which is more structural because of that rigidity and because of how it links the front and rear of the car with the seats mounted directly on the battery. See the video below. This type of design could be better for a swap or worse. I don't know. If they are doing the same pack size then the interior of the battery might just have more filling material/adhesives in place of batteries, so if that is the case then the older batteries would be ideal, but maybe it would be still easier to use an older pack in this type of cutaway for a swap. I don't know. The future will see what makes an ideal swap.