Chevy & GMC Vans

If I were to get a digital cluster for my 89, would it fit and work without any crazy wiring?

You have a mechanical speedo. Guess what? It won't work.

No, an 89 has the electric speedometer; 88 was the last year of the cable driven speedometers. I own both an 89 and an 88 and that's the way things are with them. My 89 has the digital dash and I'm frankly unimpressed. Saying "digital" is a bit of a stretch, though, as only the speedometer is digital by my definition. It has digits that change with the speed, but all the other gauges are LED bargraphs and they drive me nuts. I'd much prefer 270 degree sweep analog gauges for everything.

Scooby, your question has come up before, several years back if I remember correctly. I'm going from memory here now. The digital dash uses different backplane connectors than does the analog one, but the connectors are on a short cable that can be plugged into the main dash harness of the Astro. The plastic outer trim piece for the digital gauge is different from the analog one, too.
Your best bet for conversion to digital would be to find a junked 89 digital equipped Astro/Safari and remove its gauge assembly, trim piece, and the short wiring harness.

One other thing though. The digital gauge set, at least in my 89, can be very intermittent. It's not unusual for the entire gauge set to go dark while driving with only the temp gauge somewhat working (I say "somewhat" because the temp gauge looks as though it's caught between the Farenheit and Celsius display mode). The quick fix is to shut the key off and then turn it back on; this straightens out the display for awhile. Not sure what causes this problem; one of these days I'll yank the gauge set and resolder all the connections on the backplane.
Another very common problem with the 89 digital gauge set is for the temperature gauge to flicker crazily. This is easy to fix by resoldering all the connections around the temperature gauge area. I had to do this on mine.

My bad.