When i turn on the head light it doest light up

Probably the fuse if it is OK then check the break light switch.

radio, as radio lights? the light switch could be bad

Most likely cause is the head gasket ,its pressurising the cooling system

check for ignition fusible link near the battery .It may be blown

hi sounds like you got a coolant problem (ie ) head gasket have it checked but first check water level

You may have a head gasket leaking. Head gaskets can leak two different ways. One is to the exterior. You will see it and it will be quite obvious. The other is a water leak into the cylinder. the water gets into the oil pan via that route. Do you see water or steam (looks like white smoke) issuing from your tailpipes?

you should remove the starter,take it to local parts store to have it tested. it might just be stuck

Check grounding at start of the wires coming from under the truck you will proble find a corried ground wire whitch cause afeed back to other lights thus completing circuit.

do you mean 420, because alot of times the code does not directly indicate the cat is bad. other factors have to be ruled out before replacing the catalytic converter. Expensive mistake when you skip getting it diagnosed correctly.
But since you did replace it your suppose to have the light turned of with a scanner or code reader if you didnt do it yet. The light will take up to a month to shut off if it doest see the problem again if you wait.

make sure you have power getting to your starter when you crank. check the small nut on the starter. should have 12 v or very close to it. this will tell you if your getting power to the starter or if somethign before the starter and something maybe with your anti theft system or not. its hard to say online cause of that anti theft. doest the light flash at all? the anti theft light?

if your getting power to the starter when you crank make sure your getting good power to the starter by turning on the head lights and see if they dim. a good starter will cause the headlites to dim when attempting to start. if nothing dims check connections. or assume bad starter motor. make sure your also getting power to the main starter stud as well.

good luck
michael