Hello. I am upgrading my radio on my 1970 Plymouth GTX. I would like to use one of those RetroSound speakers for the front dash. What size would you recommend and how would it fit? I don't have an AC in the cars (the windows are the AC, haha). Thanks in advance.

If you have the orig 8 ohm factory radio, call these guys. I used their hi perf 8 ohm speakers in my Challenger with the 3 speaker dash option & orig am 8 track & the sound was awesome. They also make a front center speaker housing with two smaller 8 ohm speakers.
http://turnswitch.com/speakers.htm

I used two of the RetroSound 3.5 inch speakers. Bought an aluminum plate with the two holes for the speakers, but you could use medium density of fiberboard (MDF) and cut out your own. See attached link where I show several pics of the install in my 71 Roadrunner.
Ron



http://www.roadrunnernest.com/forum/viewtopic.php?f=2&t=4431&hilit=RetroSound

what speakers did you use in the front? every 3 1/2 i've tried sounds like a tin box.

I used the RetroSound 3.5". It's a fair sounding speaker. The best would problablty be the Infinity reference speakers, but they are costly. Then, no 3.5 " speaker is going to provide bass like a 6 x 9 speaker. It basically will supply treble and midrange frequencies. There's just not much room in the opening provided in the dash of a 71 B-body. You might be able to fit ( with mods to the speaker) a 4 x 10 with the dual voice coils.
Ron

Before recommending speakers U need to confirm what is the radio upgrade?
Many posts have said use 8 Ohm speakers..
But if U are upgrading to a later radio, these typically use 4 Ohm speakers so if one connects 8 Ohm speakers U will lose 50% of radio's power output...

Clarify what the radio upgrade is and we will post more options. Note that we are an MECP certified engineer and have built multiple SEMA and CES magazine show vehicles.

Just my $0.02..