If your 5.7 was a throttle body, the two red leads into the injectors are a good source. Route one through the temp sender on the passenger side head and then to your cold start valve. Use the other to energize the pump. Both are switched and are big enough to handle the amps.
Brakes are another thing. Does your truck already have the hydro- boost brakes or are they vacuum? If they are vacuum brakes I would suggest you find a hydro-boost system. You can run them with the vacuum pump but they are problematic unless you have a BIG vacuum reservoir (70s era Ford cars had a thing that looked like a big soup can under the hood for vacuum. That's what I used)and a good check valve.
Bill
91 Buick Roadmaster/Avant 6.2 NA conversion (gone but not forgotten)
94 Cadillac Fleetwood (sold)
08 Aerolight 23TT
06 Vortec Max Silverado CC SB (sold)
10 Avalanche (electronic quagmire but love the truck)