Are you losing anything other than just spark when it dies? Obviously if JUST spark then it's something in the ignition circuit, but if anything else happens to loose power, maybe you have a fusible link/fuse/power distribution circuit issue.
If definitely just ignition, tried wiggling the wires that feed the distributor, coil, etc.? Another thing I'd check/swap are whatever fuses the ignition is on at the fuse panel...obviously won't be popped, but maybe corrosion, loose contacts, fuse that is coming apart, etc.
If definitely just ignition, tried wiggling the wires that feed the distributor, coil, etc.? Another thing I'd check/swap are whatever fuses the ignition is on at the fuse panel...obviously won't be popped, but maybe corrosion, loose contacts, fuse that is coming apart, etc.