#1 is the first one next to the thermo housing. #6 would be the one at the back. There is no way to find out your exact advance unless you have a really expensive indexing timing light. Just keep crank it forward until it starts to ping then back it off. Dont you have a Haynes manual or an OEM book? Dont take this the wrong way but if you are asking stuff like this then why are you even considering the tires you posted about? SOunds to me you need to take a step back and learn a bit about your truck.
i do have the manual but it's not at my house.
my motor has ran great in the past, but something is starting to slide.
i'm about to rebuild my carb, but before i did i wanted to make sure my timing was ok.
for some reason when i stomp on it, it cuts out and trys to die.
i was hoping it wasn't my advance... and it wasn't. my carb seems to let the motor run to rich or to lean through the whole rpm range. hopefully the rebuild will cure the problem. i've already been informed that it's been jetted for my altitude.
anyway, i've never had to time it before (though i've owned the truck for about 10 years now. i just had a DUI installed and wanted to double check what the mech had setup.
You can get an indexed timing light for about $20 at NAPA or Harbor Freight. Or just borrow one from NAPA, Advance or corner shop.
When you have the light hooked to the #1 cylinder and the light pointed at the window to the flywheel, the silver "BB" will line up with the pointer when you are at 7 deg BTDC. I have a DUI in my 74 1.5F and I have it set to 11 degrees BTDC.