My Thoughts
I was not aware that the WE4 was available in any other year than 1987.
Is this to say that you are going to convert this to a WE4 along with the intercooled engine? Just curious.
The value depends on the overall condition and the quality of the coversion. If it looks or runs poorly it detracts from the value. Are you going to sell it after the conversion? If so I wouldn't bother to convert. Too much hassle for the $ to be earned. If it is being built for you to enjoy then you get a knowlege of how things went together for when you get to fix it.