FYI - that pillar is structural and designated as a no-cut zone, as far as the BEMM specifies in order to maintain roof crush strength for rollovers.
That said… if that’s not a concern for you, and it being a body-on-frame vehicle… the van won’t far apart. If I wanted to cut a holt like that, I would drill out the corners with a regular drill bit, then cut in between with a cutoff wheel. This will avoid any sharp notches that could cause later cracking.
2000 E450 dually V10 wagon