That will depend on your budget and what you want out of your truck. I am converting my 2.5 over to BL as we speak. Here's what I did:
1. Changed over stock diffs/cases to hybrid bulks and 1/8 diffs. stock diffs will not hold up to brushless power
http://www.rc-monster.com/proddetail...LM18700&cat=31
2. Got rid of the 2 speed and am putting in a center diff w/ a custom motor mount Mike will be making me.
3. I am using Hot Bodies hardened diffs front and rear
http://www.rc-monster.com/proddetail...GY_DIFF&cat=40
4. FLM extended E-Maxx chassis
http://www.rc-monster.com/proddetail...chassis&cat=31
5. I will be getting the FLM towers as well when money permits.
6. MMM esc
7. Neu motor... 1515 2.5D ....soon
If you want any other ideas, just let me know...

Bottom line is that if you want quality, it comes w/ a price. Save up if you have to to do it right the first time
1. MBX-6 T8 1900KV, RX8 ON 4S
2. MBX-5T 1520, MMM ON 5S
3. MBX-5 ONROAD CONVERSION 1515, MMM ON 5S
4. MRX-3 ON ROAD CONVERSION 1512, MMM ON 6S
5. TEN T 2650 T8, MMP ON 3S