You really can't add it.
The burst and SEF packs are very different from each other. If you have SEF and want burst. You buy a semi-auto burst pack and send your SEF/w sear and burst pack off to your favorite dealer along with a check for the labor =). The dealer then sends back your FA converted burst pack. More sear ready packs than sears is a no-no, so the dealer keeps the SEF pack.