Another suggestion: Pull the valve covers, give each valve a small tap with a rubber mallet, make sure they move or are free (after 20yrs they may be stuck). I once tried to fire an old 389, some of the valves were stuck and when I went to try and fire it I bent some push rods. For the longest time I couldnt figure out why the engine wouldnt fire until I pulled the valve covers, had someone crank the engine and noticed that some of the rockers were not pushing moving due to the push rods being bent! I gave those valves a couple of good hits to break the freeze, re-installed some newer 389 push rods and she fired off!! (still had to rebuild the engine because of the mileage however). Just another thing to consider before turning over an engine that has been sitting for soooooo long...

pull the distributor and pre-oil the engine (prob should change the oil & filter first). Also pull the plugs and shoot some light oil in there (Marvel Mystery Oil, WD40, etc) Then rotate engine slowly by hand making sure it is free. After all this, fire it up.....