Late model radio in 91 roadmaster

Want to know if anyone has tried this: The opening for the radio in my 91 is 1.5 din and there aren't many aftermarket CD players in that size. GM has made a billion factory Delco CD players for the same size hole over the years (still making them) and they are certainly good enough quality for me, but has anyone tried to hook one them up in the older cars? They talk about 21 pin or 12 pin connectors, but I'm unfamiliar with these particular units. The Delco's from 2000 or so on have lots of features and are dirt cheap so I'd like to get something like that if someone had some info on the swap.

Umm.... I dont know the exact specs. But I do know that radio installers can install the Plug for the stereo if someone had wired in a stereo without using a wiring harness (adapter) (tsk tsk)..... If you baught the end for the stereo, and then just baught a wiring harness adapter, you should be able to do it...
(a diagram kind of..)
[NEW STEREO] } ^^ ^*^ { [old stereo would be here ]

(Key:
} , { = plug, ^^ = wiring harness (adapter) ^*^ = wiring harness (adapter) for your car )
Bill