Starter issues !!!! Long start then nothing help!!!!!!

[MrOrange]

So i have been fighting this issue for about a week or so. Just purchased this 1970 cst10 truck , never did i have an issue with the cranking or running of it. As i started to drive the truck more frequently i noticed that the starter would have a longer and longer crank . I decided to replace the starter . This is when it all went to hell. now it doesn't crank at all unless there is a massive amperage sent to it ( my battery charger on start) and sometimes that doesn't work. The battery wire to the starter was getting real hot to i changed it over to a new 4 gauge. still same problem . Now there is a buzzing electrical noise coming from under the dash. I isolated it to a relay which i cant identify what it goes to. it was wrapped in a cardboard cover and has 2 separate pigtails one is brown and one is black. Any help would be much appreciated.