you should be able to pull this off with very basic tools. old recordings had a crappy frequency footprint - very poor representation in upper highs, a lot of over representation in midrange frequencies. there tended to be a lot of analog distortion to the signal as well, but i think the trick that will get you the most leverage is applying your vinyl/tape distortion *after* the room reverb. distorted reverbs sound *way* crappier than reverbed distortions (which can sound quite pristine with good reverbs) - and crappy is what you're going for!

i would try something like:

boost around 2kHz -> cut above 4kHz -> room reverb -> tape/vinyl distortion (add some subtle vinyl static if you want)

the 2-4kHz range contains the bulk of the consonant information (e.g. non-vowel vocalizations) - you will probably want to play with this range to soften the consonants in order to lo-fi the recording to 1950's standards. the 4-6kHz can bring out clarity and presence - you will want to make sure these are attenuated also.