1972 c20 master cylinder - no match

[Aruba1]

Hi everyone, after an hour seatching through the search function and not being able to get an answer I decided to post a thread :-).

My truck is a 1972 gmc c20 with stock disk brakes. My brake booster went bad so i ordered a brake booster and a master cyl for my truck with disk brakes. The MC has the holes switched, large hole in the front. Should i install this and reroute the lines or should i search for the correct one? Any hint on how to trave the correct part? It almost look like the c10 MC should fit.

Also upgraded the brakes to a 1989 c3500 system (front and rear). Should I get the year correct MC and booster setup for my truck? Thanks