The STM kit says it adapts to the factory sending unit and fuel rail, but it's not clear how. I tried searching online for someone who's used the kit, but came up with noting. If you go that route, make sure you verify it will connect up to the flared fitting on the pump outlet. I don't see a provision for that in the kit picture on their website.
As far as the brake lines go, iceman has it right. That's going to be a shitty job no matter how you cut it. Personally, I'd run all new lines. I definitely wouldn't run splices with compression fittings. Splices with new fittings/flares would be my last resort. I'd say grab a roll of line, some new fittings and a tubing bender and go to work. Make sure you clean up any of the rusty brackets you'll be reusing that secure the lines in place. Usually the rusty bracket coupled with the rubber holder traps moisture and grime against the line, which is usually where leaks occur. The crusty brackets/holders will accelerate the rusting process and you'll be right back at square one before you know it.
Do you see now why everyone was busting your balls about the rust on that RS? That shit will bite you in the ass every time if left unchecked