My guess, well I have many.
Check the throttle sensor, make sure you hear 20 clicks as you move it by hand (its kinda fun
Check the fuel pressue at one of the injectors. Just pull it off and fill a 20 ouncer with some gas. Crank it for 5 seconds, and the ouncer should have 1/3 full of gas. Make sure to dispose of this gas correctly (i.e. dont drink it), maybe dump it back into your tank if the 20 ouncer was clean. Then rinse out the pop bottle. If you have enough fuel in here, you should be fine. If it was pressure related from hooking it up backwards, it will not run.
Also, check your points. I think you need a tune up, plugs/wires/points (or equivlant). Set the timming.
Hope any of this helps.