wbs is correct there isnt a cd/tape deck radio that will work for your Pontiac/GMC/Chevy. Buick/Olds does have one but the connector is different than that in your Pontiac(and IMO quite ugly), I think the buick/olds radio may be a 2 din model as well. you may want to try a pontiac Tape player with a remote CD player or A cd player with remote Tape deck.If you are going to do this ensure that the radio is capable of running a "remote" unit, some dont have this circuitry in the radios.
Why would you want to play tapes anyway..it is so much easier to copy it to CD.
and thats my $.02