what are the best componets that you can put in bravo xr sportmaster to make it last from top to bottom?

Simple, easy on the throttles and hole shots. You might get 50-100 hours between rebuilds. The Bravo gears are junk and won't hold up under much high HP engine power. Even going to Imcos, they all use Bravo gears except if you want to spring for the Imco SCX uppers and SC lowers which seem to be the hot setup for now. I'm in the same boat so to speak.

Bravo XR upper gears have had a problem breaking teeth off. It used to be years ago that you could get 250hrs out of a set of upper or lower gears. These days they can start to give off metal in a few hours.
The SCX has larger and harder gears. Using the SC lower gives you Merc gears and still prone to early failure. The SC lower is used due to the size of the SCX lower and it's larger gears.
It all depends on what you want.. Longevity and have to deal with setup and possibly some speed loss or have to keep a close eye on the lower gear set so it doesnt contaminate the SCX upper.
How you drive is a major factor. But to name components to put in an XR, they all come from Merc, execpt for shafts. There are caged bearings, claim to run cooler, but have less load capacity. Making sure the towers are aligned and proper setup is a big factor. Cryo and polishing treatment does show some improvement in some cases, but it doesn't fix a bad gear.
Hope that helps.
Dick

What power do you have?

500 efi with wipples