I have Nostalgic AC units in 2 of my trucks...they're great. One is in a 45 pickup so that's not very hard to cool down. It does a great job. Just put one in an 45LV....have not had to put it on yet.....still windows down driving. That one will probably struggle to cool that cabin....big truck. Install is really nice and the people at Nostalgic are great. Check out my 45LV build thread(in my signature) and you can see how I did that one....they made it special without any control knobs on it so I could mount them in existing holes in the dash. Looks really cool and they take up very little passenger space.
We had a FJ43 in the shop last week with a Vintage air and it took up a TON of passenger area space. That really bugs me on those units.
Have you looked at Old Air? Currently fitting one of their systems in a customers FJ40. Really nice unit(looks cool because it goes where the heater was) and some really cool options with regards to controlling it. Easier to call them vs. trying to figure out their website offerings...it's a little confusing. I think it's probably going to be the best out of all of them.
If I had a complaint about the Nostalgic Air units....they get a little buzzy on the higher speeds. You really need to make substantial brackets to keep them tightly mounted.
Consider lining your floors and firewall with Lizard Skin's sound deadner followed by their ceramic insulation. That stuff is amazing. And make sure that firewall is really sealed up along with your shifters and trans tunnel. You don't want any of that hot engine compartment air sneaking in the cab.