Is it possible to swap the basic Hitachi head unit from a 1984 model to the Technics/Panasonic factory head unit with the equalizer without creating a huge mess? Size wise it looks like it would fit. Has anyone attempted this swap before?

I haven't heard of anybody doing this but gotta ask are you just trying to keep things looking stock? I bailed on that Hitachi in my 84 after it had 4 repairs early on and then cassette deck died in 94'. If the Panasonic unit has be refribished then I would perhaps trust it but I never looked back after doing a rewite with great speakers and Alpine AMP and changed the head unit again in 05' to one with iPOD. The sound is night and day better and how many cassets do you own now?

I was hoping to keep things looking as stock as possible. The stock unit leaves quite a bit to be desired. I kind of started getting back into cassette tapes again since that was the format I grew up with. Don't have lots of tapes but it is nostalgic for me. Was hoping to add Bluetooth, maybe a cd changer and 2 old school MTX Blue Thunder amps still in the box and an electronic crossover I had with them from back in the day. I have 2 sets of high end 6.5" Alpine separates to put in the front doors and in shock tower opening in back. Maybe even a small sub at some point. Would probably be easier to just buy an old Blaupunkt, Kenwood or Alpine tape deck from that era instead of messing with the old Hitachi unit.

Yes, at this point if you wanted to go cassette that would be the way to do it, these stock units are terrible at the end of the day. Also, you will need to rewire the speakers as the stock power amp is probably toast, i took that big plunge in 94' initially, adding Kenwood speakers (they still sound great to this day) with an Alpine 4 way AMP tucked under the passenger seat and yes a bazooka tube in the way back (neatly) powered by another Alpine AMP. Initially I added a Kenwood CD Changer controller that was replaced about 10 years later by an Alpine deck that was just before bluetooth so used iPOD. I am waiting for that to die so I can add streaming but I have over 900 albums on the iPOD and that is the only useful thing that iPOD does (I cannot believe it still works). the big expense is the speakers and rewiring to a new AMP. If you really want to stick with cassette you will need to find a re-worked unit nobody makes those anymore, if I were you I would do a simple looking single DIN steaming radio....the stock radio is just so crappy...but if you did one make sure it is completely refurbished because quality of those units was bad. The Hitachi lasted 10 years but was replaced by Nissan 2-3 times under warranty