RadioStereoTapeCD
What is DIN when it comes to car radios, look HERE.
Basically it breaks down like this:
DIN is a standard radio, and while not official, double DIN is twice as high, and 1.5DIN is the weird size that GM used in the late 80s, 90s, and early 2000s so as not to be compatible with anything else on the market(insert middle finger emoji here).
The factory radios on the A/S vans are "1.5DIN", which is an odd size and a very limited selection of available radios. There are adapters for single DIN (180 x 50 mm panel), and you can make a double DIN(180 x 100 mm panel) fit by modifying the mount and dash.
There is a new Metro kit designed for an easier 2DIN installation into our vans.
Without the wiring harness https://amzn.to/332TXj4
With the wiring harness and antenna adapter https://amzn.to/33d6EYR
Here are a few examples of Double DIN installations in an Astro/Safari van:
https://www.astrosafari.com/viewtopic.php?f=127&t=115353&start=540#p1420786
Using a single DIN flip up and moving the HVAC controls http://www.astrosafari.com/viewtopic.php?f=13&t=122409
Maptech enterprises makes really nice custom adapters, check out their website at http://humount.com
DIY Aux Input:
You may want to add an AUX input to your factory radio, this can be done quite cheaply.
$3 AUX input on factory built in CD-radio http://www.astrosafari.com/viewtopic.php?f=32&t=23577
You can also do the same thing with the wiring between the slave CD/tape player if you have one. Would have to have a working slave unit, and a CD/Tape to be present in the slave unit for it to work.
Pin Description Color
1 +12vdc - Orange
2 Data - Dk. Green
3 Ground - Black
4 Audio Common - Lt. Brown
5 Left - Orange Blk Stripe
6 Right - Lt. Green
7 Voice??? - Clear
8 Dimming - Gray
9 R14??? - Blue
WimpTech did a similar but fancy setup here https://www.astrosafari.com/viewtopic.php?f=32&t=111441#p1141169
Here is the speaker wiring diagram for an 03 without RSA.
Replacing the factory radio with a new one is quite easy, esp if you get a wiring adatper/harness instead of cutting the factory connector off. Don't be a douch and cut the connector off of the factory harness.
Get something like this: http://amzn.to/2owBxq4 which you then solder/heat-shrink or crimp onto the new wiring/connector that goes to your new radio.
1985-2005 Chevrolet Astro Stereo Wiring Colors(this should be standard, if any doubt - TEST)
Constant 12V+ Orange
Switched 12V+ Yellow
Ground Black
Illumination Gray
Dimmer Brown
Left Front (+) Tan
Left Front (-) Gray
Right Front (+) Light Green
Right Front (-) Dark Green
Left Rear (+) Brown
Left Rear (-) Yellow
Right Rear (+) Dark Blue
Right Rear (-) Light Blue
One of my favorite sites for car audio/electronics is https://www.the12volt.com check it out, they have some great info on there.