Starter turns over and starts as soon as i let off the key it kills Ive change the starter silinoid and it still dousnt work

The ballast resistor is bad or the ingtion swich is. witrh the key on their shold be power at the ingtion coil. if not check at the ballast resistior it shoud show a test light on all terminals. with slightly different brightness. jumper wire to the positive on the coil from the battery positive shold keep it running. find the broken wire or the bad part with the test light. the starter solind only turns on the spark while cranking. even the key switch can be bad or the wire coming from it.

Ignition switch is bad on the steering column under the dash it's a rectangle box with a bunch of wires connected to it also has a metal rod going up to the key switch I have replace several of these

Another solution would be to check the float in the Carburetor if it's been sitting for awhile varnish could have made this float stick. Tap the Carburetor with a hammer and see if it works.