85 silverado wont start

[85silverbeast]

I bought a 1985 chevy silverado 2wd swb 350 about a week ago, the starter didnt work I replaced it and it ran good for two days and for the past 3 days or so it wont even crank, the battery is good i replaced the terminals and all the lights and accesories turn on. What could it be? Thanks in advance for any help and advice im new to this trucks I used to own a 1994 mustang gt up until 3 weeks ago when i wrecked it.