The key is to use it sparingly. With audio, more is not always better.
There's a big difference from recording +5dB on a reel of tape and +5dB on a digital system. On a digital system, it will get raspy and scratchy REALLY fast. On tape it won't really get to a full squared off wave due to limitations in HF recording ability and the ability of the heads to handle the slew rate being thrown at it.
Assuming that the recordings were done via tape in the 80s (not necessarily true as Soundstream digital recordings were starting to come online around 1980, especially with classical recordings), then you need to imitate that tape limitation. The way to make the volume more constant is to compress the signal, and magnetic tape will do some of that automatically.
I threw out those plugins because they are free, so you can play around with them without forking over hundreds of $$ just to find out that they are trying to imitate a Marshall stack at full song, not an overdriven mic preamp in a Trident console driving a 24 track Studer chewing up 2 inch tape at 30ips. (ok, if it was a low budget film, they probably ran it at 15ips
)
You might also do some research into film based audio. Search out "Academy Curve" and you might understand why the EQ curve I posted is starting to sound like what you want. Remember that in the 80s, most movies still used optical audio tracks which are limited compared to CD/DVD audio capabilities. The advent of THX, Dolby DTS and the like have changed the audio portion of movies. Now that film has been replaced with digital prints, things have changed, although there are still some remaining standards for theater audio reproduction.