Good answers so far. Not enough history to guess better, but one factor on a 27-year-old motor could be wear- if you don't have compression, it'll crank fine but won't start. Did you do a compression test?
Timing is another thing that could be wrong. That old 460 has a timing chain, right? If it's got a lot of miles, the timing chain could be worn, causing the chain to jump a tooth. In that case, you'll never be able to get the timing right. You can check by taking off one rocker cover, pulling the plug and put something like a pencil in the hole while you slowly turn the motor over by hand. (That 460 will require a bit of muscle to turn over. Do not, not, NOT try to crank it with the battery.) Watch the valves- they should both be closed just before the pencil sticks out the most at TDC. If the valves both close after TDC, you've got timing problems.
One standard thing to do- get a repair manual and read the troubleshooting chapter. No matter how well you know cars, the manual is a great reference. Take care!!