In 1983 I was on a quest to build my own single humbucker strat like EVH's and I definitely recall that it was an ash replacement body that he used. The closest thing I could find at the time was an ash body by DiMarzio. I remember being disappointed that it wasn't exactly what EVH used, but it turned out to be a fantastic body. I wish I had bought 10 of them. I went through a couple of necks until I got a hold of a very flat radius Charvell neck with large frets in about 1984 or 1985. I'm still playing that exact guitar today - great neck, regular ash body, a Floyd Rose, and a good pickup. That's really all you need. And a lot of time getting the setup just right of course.
I tried to build a guitar using the lighter ash in the 1990's with a pre-painted ESP body and it looked great but was worthless as an instrument.
If you build a project guitar, try to find an ash body that has the look and feel of an ash baseball bat.
Paul