I have a friend who installed them on his G 4x4 and he said compared to his friends that he’s driven after installing his it makes a noticeable difference. He’s got 15x10 steel wheels plus 35” tires so it’s a considerable amount of weight so he has confident brakes and that goes along way in a van.
In general it’s a pretty straight forward install and I’m sure with some research online, you can find all the info you need but I found this video to atleast show you what you’re getting into.https://youtu.be/PJpC0W6CP78
I have looked at this before too and know from that time of research for a GM van, you can also look at OEM GM parts like Astro vans which share 5x5 bolt patterns as well as late 90s RWD Impala models. If you want a kit, I found it easier to search with C10/20 5 lug models since there is generally a larger audience for those parts and many companies that sell parts for the trucks.
For me personally I decided to not do it only because I rarely drive fast enough or haven’t been in situations where I didn’t feel like the stock brakes didn’t work well enough but I’ll leave that decision up to your discretion.