Btw, the “tried n true “ chalk mark test is about the worst way to figure it out unless one can’t envision what gross over or under inflation looks like.
Either go hit a truck scale or do a little math based on Uvw, anticipated axle loads and a good guesstimate of how much ccc you’re using. And what your tire load capacities are.
Not rocket surgery and not that difficult.
You’ll find 65 is probably right for little tires under a big van steer axle.
The right rear pressure could be all over the board. But higher than necessary is safer than lower than necessary.
But you have to do your own math. We can’t invent the math without the numbers