I don't think you can go wrong with DOT-5 Silicone. I have used silicone brake fluid for at least 20 years in various vehicles. The main advantage is that it does not absorb water and ruin your seals and cylinders. The main drawback is that it does not work well if regular brake fluid was present in the system. I replace all rubber lines. The ones I did not replace swelled up from the inside and eventually would not allow fluid to pass. I don't know if the blame lies with silocone or some other factor. When I redo a system that has had regular brake fluid in it, I flush it with denatured alcohol before I start rebuilding. That cleans out the steel lines without contaminating the rebuilt components and new rubber lines. I agree with Mr. Pushbutton's comments with bleading. I have noticed that it may take several months before the fluid level stabilizes. Unless there are visible leaks, just keep adding fluid. I think the GT model of MGB is one of the best looking sports cars around.