I've done the same conversion with the brackets bought on ebay. Everything fit fine. But now I'm having a problem with my brake pedal sinking all the way to the bottom of the floor if the booster lines are hooked up.
Here is what I did so far:
I changed out the master cylinder to a new 280zx, new brake booster and rebuilt back drum setup completely. I've bleed the master on a bench (I think I did it correctly, don't know if I pushed the rod in far enough), but did the "two tubes back in the reservoir, till no bubbles" thing. Bleed the brake system with a friend, two man system, on all the brake lines with no bubbles. Pedal doesn't get firm till about almost half way down with the truck off (no booster assist), with the truck running, the pedal sinks to the floor. It does grab the brakes when at the bottom but not convincingly.
I don't know what else to do. Any tips on what to double/triple check again would be much appreciated as this has got me stumped.
I was reading on other forums that there are two different types of Master Cylinders, one that is made for a brake booster and one that is non-booster? Is this correct and could this be the problem?