Don't get overwhelmed with the brake lines they're not that complicated.
Are you using the master cylinder off of the '84 you got? do you have the proportioning valve and lines from the '84 also? If so just follow the layout of the factory '84 lines. I've seen guys use the newer lines on the older trucks and it doesn't look bad. You may need to add a bracket underneath the radiator crossmember to bolt the prop valve to.
If you don't have the '84 prop valve then just do as protrash64 suggested and just run an adjustable prop valve in the rear line. The writeup that Chiefrocka did on the brake lines is really good and should answer most questions for you, if not we're here for ya.