If it is a 1998 E-250 V8...no 4ad...nothing special there other than the fold down bed.
*Do a leak down test to see if cylinder heads leak...you'll need to see what major electrical and maintenance work done.
ImHO start talking at $12 - 14K. You need much more info. Certainly a project to build out.
Now.... If it had say a (Quigly 4 WD system) you add 10 K at that year model..
Aluminess front or rear bumpers add $2K each (then depreciation) depending on condition/maintenance/ years.
west coast or east coast matters little...its really what YOU the buyer are willing to pay and what is out there and how well kept and maintained the E 250 is in Oregon.