What size speakers are in my 83 300d?
 

Replaced a crappy cd with a new one.

Now 26 yo speakers don't sound too good.

I bought a pair of 5 1/4" Jensen's off ebay for the rear.

What speaker has anyone replaced for the 4" in front?

I've got a pair of boston acoustics S45s in the front. They fit well, but you'll have to trim off one or two of the mounting "ears"

I just ordered a pair of Pioneer Premier TS-D402P 4" 2-way speakers for the front and a pair of: JL Audio C2-525x 5-1/4" 2-way speakers for the back. The front will fit under the factory grills with no modifications, the backs will require re-drilling the mounting holes.

Just installed my new Pioneer Premier TS-D402P 4" 2-way Speaker's in the front and boy do they sound great! They also fit under the dash grills! Sure beats the paper factory speakers... now I just need to do the back speakers tomorrow night or Friday with the 5-1/4" JL Audio C2-525x 2-way Speakers (but they will require some drilling and possible modification of the speaker mounting to fit under the factory grills) might just use the JL grilles for awhile... anyway here are some pictures...

I have the alpine 4 inchers under my front grilles and they are awsome, i think i like just as much as my JL'S.