convert to dual master cyl

[Vnotchback]

going to change out my single master cyl i have disc brakes all around pedal is hard bought it this way just want to know if there maybe and surprises doing it

[Marc]

Besides the M/C you're going to need at least one different hardline (the only dual M/C on the market is late-style and requires a pipe replacement even when used to replace an early-style dual M/C)...can't recall the exact P/Ns off the top of my head, I'll have to do some research if nobody else chimes in.
Of course you realize that you'll also need the dual reservoir, its mounting cradle and the feed lines - this is where a donor car would come in handy.
If you aren't concerned about having a brake-system warning light on the dash there's no need to buy the three-prong brakelight switches; the two-prong from your old M/C and another one like it will suffice (simply add two short wires to place them in parallel).

[Vnotchback]

Sorry didn't mention it is a notch back but yes right about the reservoir and lines thanks for the info

[Marc]

Sorry didn't mention it is a notch back...

I sorta guessed that from your moniker
Back in the day, when the 311 611 015J became the only replacement M/C available, we used to buy the needed front brake pipe from the local VW dealer, already bent to the correct shape. Can't find the only parts book I have which might contain the part number...but if you can bend the line(s) yourself, you should be OK just purchasing whatever's sold for a `73 (straight pipe that's the correct length, may not have a 311 part number).