had battery tested fully loaded.truck starts up just fine then after going less than a mile just quits. will start back up after 15 to 20 minutes. Do not know what to do. Any ideas?

See my post on a similar problem several posts below titled 1988 F250 460 EFI INTERMITTANT STALLING.
Jim

Maybe it over heats or you have a short.

well, do you still have spark? When it dies pull a plug wire off and see if you still have spark, if you don't could be the CPS sensor, the computer, or the coil. If you do, chances are you are not getting fuel. Push the pressure releif valve on the fuel rail coming up to the engine and see if you have pressure, if you don't, it could be a bad pump, regulator. If you still have pressure and spark when it dies, could be a CPS sensor, or temp sending unit ( telling the PCM it is warm when it is still cold)

Just solved my similar problem with 1988 f250 460...I replaced the TFI module and pickup....just because they were original and 16 yrs. old. They never should have lasted that long as Ford had a lot of problems with TFI modules....anyhow, my problem went away!