I had my truck running and then I shut it off and it won't start back. I have changed the starter and alternator and checked the battery. Can anyone help?

no it doesn't turn over and yes I still have points. Mine is a 1974 that originally had an L18 but I put a L20 from a 1977 in it. I tried starting it and it wouldn't run very long so I put some gas in and turn the distributor and it started running fine and then I shut it off to make sure it would start with the distributor turned the way it was and I got nothing no turning over no clicking so I assumed it was something electrical so I put a tester on the battery and my connections to my starter everything was fine except I'm not getting power to my ignition switch and I don'y know why. I am supposed to have power coming to the switch right?

THIS WAS THE ORIGINAL ENGINE

youd better put a socket and breaker bar on the front of that motor and see if itll turn over by hand. hope you didnt lock up you motor...

I just rebuilt the motor it is'nt locked up. My dad drove one of these trucks all my life and I'm 21 now. I think he had it before me actually. That's the main reason I bought the truck 'cause I grew up ridin in it and I actually learned to drive in his. Luckily he knew exactly what it was he put a tester on it and sure enough the fusible link was melted inside where the fuse makes contact. I changed it out and it started right up. Bad part is the second one burnt up too. I'm gonna get a heavier duty one tomorrow. Thanks for the help