1968 390 gt oil leaks

For the paint restoration, I have used this guys method before.  It is a lot of work, but it does work very well.

Also-- anybody have a good go to setup for polishing the original single stage paint? The paint is really in pretty amazing shape, however there are spots of oxidation and some water spots I would love to be able to remove. I am a bit hesitant to dive in as I don't want to remove too much while doing this.  

or it had the wrong master on it?

i realized something when i wasn't even trying, i think the reason the leaking line is all bent out of shape is because you have the wrong master on the car. if i'm right your original master had the line coming out of the unused boss on the side like the rear line, not the down schnozzle. i read somewhere why the masters are different but that brain cell took a leave, it may have been hardtop / convertible or something to do with the brake config whether they're manual drum, power drum, manual disc/drum or power disc/drum i forget but there's a reason the master was different from the factory. different applications

what is your brake configuration?

or it could just be bent

I have read about fluid migrating into the booster, however I feel the mechanic should have noticed this. I'm really thinking about replacing it all at this point (booster, MC, lines, etc). 

so much for the good mechanic. replacing a master on a 1968 anything should've included the lines to the prop valve, just because.

you can see that the line is tweaked from the 1st try at loosening it, the 1st thing i'd do is loosen the tube nut and try to correct the angle of the line coming out of the master. it should be coming out straight down rather than the 10* angle it is now. hopefully the flare in the old line will reseal once it's put back straight.

next worst case you buy a short brake line with ends formed and nuts installed and bend it yourself, it's easy

next worst case you get yourself a complete brake line kit and install it yourself, or by a slightly better mechanic. this is one source, there are others
https://www.inlinetube.com/pages/product-list?year=4212202341531695823&make=1828299879717471912&model=4907562634040960157#?f=6883668340566495367|

if you don't have them, buy a couple tubing wrenches that cover the sizes of tubing nuts on your car or just grab a set. if you're going to replace a line straight away, just cut the tube coming out of the tube nut and use a 6 point socket rather than dick with the wrenches. a good pair of diagonal cutters will do the trick and you can right on the tube nut solidly with the socket

as far as the valve cover gaskets go, if the engine runs good and you don't intend to pull the covers off for rocker lash adjustment between rounds, i'd skip the gaskets and use just RTV silicone. get the surfaces very clean and oil free and the covers will stay on with no bolts, but use the bolts to locate the covers until the RTV sets LOL. but seriously, RTV won't leak, ever, if you prep the surfaces well

relax, you got this man!

The master cylinder has seals that are simple to replace. Pull it out and return it for a new one. Once you have gone through all the brake components, you will be confident that it will stop like it is supposed to.

If it is a short line, that you could bend to shape with raw Nicopp, with the two fittings on it, take it to someone who can form the flared ends for you, and the bends of the line will allow it to fit easily. Long lines are a different matter, those usually have to be made(form the ends) in the vehicle.

I helped a friend about ten years ago with a MC swap, his 90 Lincoln LSC had a bad MC, and those are massive and complicated(TEVES brake system). One of his old lines(left front) would not come out of the MC, rounded the fitting off finally. I bought some Nicopp line locally, about three feet, and had a line bent up in about ten minutes. The ends took a good five minutes each, so the whole line was about an hour with driving to a local hydraulics business that carried the Nicopp line.