I found the data sheet on www.datasheetarchive.com. Just search for tms2564.
The two parts you listed are really the same part. The MEP8349 and RTI8323 look like datecode and fab information. The first was probably built in the 49th week of 1983 and the second in the 23rd week of 1983. I'm not sure about the 3 letter prefix, but it probably tells which fabrication plant it was built at. The JL is the package suffix, which just tells you it is a ceramic dip, and the 35 is the speed grade, 350 ns.
I'm not sure how much they are worth to people, to program them, you would probably need an EPROM programmer (you need to supply a programming voltage of 25 volts). They are probably more rare than 2764s, which I think should be drop in replacements. BG Micro has 2764s for a few dollars a piece.