dash speakers?
 

in the dash of an 86 the speakers are 3.5 inches, but i hear 4 inch will fit, true or not?

Re: dash speakers?
 

My cousin did a few years back, but IMO, I wouldn't waste any money on speakers up there. Spend the extra money on either better speakers for the doors/kicks or an amp for the speakers down there and do away with the speakers in the dash altogether.

In my S10, I didn't take this advise the first time around and replaced the speakers in there with the best speakers I could find with in my price range. Now I have a pretty decent set of a coax's in the doors with a bigger amp and tried keeping the speakers in the dash...it actually sounds much cleaner with the dash speakers completely off so I don't even run them. I'm sure if I went a step better and bought a set of components it would be killer...

Re: dash speakers?
 

To answer your question, yes they will, possibly with slight modification, depending on the basket dimensions.

Re: dash speakers?
 

I kept the stock look and replace my old 3.5" speakers with Infinity Reference 3.5" speakers (3912 cf). They fit using the same OEM speaker brackets but instead of mounting the speakers on top of the brackets, I mounted them below the brackets and use two nuts as spacers along with small stainless steel bolts to attach them. By mounting them under the brackets, there was no clearance issues when I reinstalled my dash pad. Keep in mind that if you have AC ducting on passenger side, you are limited in the depth amount of the speaker. I found that 2 nuts worked perfectly or you can cut your own spacers. Unfortunately, I did not take any photos of the install.

The 3.5" speakers sound great for their size, providing you drive an amp to them. (I went with a 4 channel amp so that I could drive both front and rear speakers.) Otherwise, the 3.5" speakers will sound too bright. Infinity speakers are known for their brightness (highs), so I added a subwoofer and a pair of 6"x9" for the rear installation.

Overall, I'm truly satisfied with the sound quality while still keeping a stock, clean look.

The other option for the front speakers would be to go with kick panels/speakers as they look great but again, you need to drive them with a separate amp, rather than driving them from the headunit. Door speakers I would stay away from since you will need to do some cutting.

And don't forget to use some sound deadening like Dynamat or Hushmat for the metal surfaces. It made a huge difference acoustically with less road noise.