They sell an aftermarket 10 bolt chevy ralley wheel. One way they are 4.75. the other pattern is 5. they will work on an astro van as for the hats n rings any chevy classic car part website should have them.

I got all the moldings off of a 99 and am gonna put them on as soon as the weather breaks

In the snow

My $500.00 95 Astro... I raised the torsion bars up front and am running 235/75-15s on american racing wheels.
Got a little rub when cutting the wheels hard. But it rides nice (and don't look like Moms mini van anymore)