http://www.97supraturbo.com/Tech%20s...0Reprogram.pdf
under the drivers seat on 98 and earlier... And some more info:
http://ww2.justanswer.com/uploads/sn...27_remotes.pdf
If the pigtail is there, it would be easier to verify the rest of the install and just plug in anything missing. If it never had the dealer installed keyless, then getting a currently made/supported system would be the smartest way to go IMHO.