1980 F-150 Doesn't Start

I just bought 80' f-150. It's a 300cid. I recharged the new batt that came with the truck along replaced the grounding wire. I have installed new Batt terminals along replacing the fuses. I'll aslo be replacing the starter relay sometime in the next couple of days when it comes in. I'm just looking for any other suggestions. any help would be greatly appreciated.

The guy I bought the truck off of, told me he drove the truck about 400 miles then shut it off. Couple of hours later he started the truck again and drove for another 30 miles then shut it off for the night. when he went out the next day (around 6:00am) it wouldn't start at all. The engine woundn't turn, not a sound nothing. I asked him if the lights or anything else work on the truck, but he just couldn't remember. It's been setting still for about 8 months now. sorry for leaving this out if you needed this info... Once again thank you for your help

[CAUTION]
Before doing any tests at the starter relay be sure it is in neutral or park.
INFO:We need more-"do the lights or any thing else work on the truck"?Is this stick or automatic?
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It's an automatic with the C-4 tranny. The interior light worked, but didn't notice anything else. I Already tried starting in Neutral as well all the other gears just incase. Nothing.

Be sure it is in park--use a jumper wire on relay from positive side to small terminal marked [S].It should crank over.By using the jumper you are eliminating ignition switch and neutral safety switch.
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Cranks now just won't start. Battery level was extemly low. I added Deionized water.

OK--Be sure you are in park-turn ignition switch to on position and crank at relay--see if it fires.

Thank you for your help. Ended up doing a tune-up and found out that buddy didn't know about changing the filters (air & fuel) and the spark plugs. Just finishing up on the tune up now.

Congratulations and happy motoring.