bergs are not hard to find parts for....buy the axles...pick a chassis...buy axial links/ends...buy tires..buy wheels (not all 2.2's will work though)...buy electronics....thats basically it...not any harder or more difficult to build or find parts for than the axial cuz really you could use every thing off a axial and just swap some berg axles in and be on your way, i would not suggest that but you could do it.
you already know what the axles are so you can right that on your list....so now go look through some chassis and see what you like and whats in your budget, i went with the ckrc rockstar chassis wich i though i might now like but actually LOVE...once you get a chassis picked out, then look for wheels, like i said not all wheels will work, even the berg wheels suck because they have the wrong offset and make it super duper wide. 8 shooters are prolly about the cheapest wheels you can get that still look good...next is tires, so many 2.2's to choose from now but i would suggest trying some of the new ones out like the HPI grabbers (i love mine) or the HB rovers. then move to buying suspension and links, depending on wich chassis you get but most will be able to use axial shocks/springs and axial links, all really cheap. RCNT vendor Eastendmachining.com has all the links you would need in many different colors and for CHEAP!!! you will also need a servo plate and mounts for the berg axles....now move to electronics, get two motors, try to get two 45t's if you can cuz they are pretty cheap but still great motors, you will also need two pinion gears. next an esc, go sidewinder or mamba max, both killer esc's and lipo freindly...next you will need a radio and reciever, if you plan on running dig you will need atleast a modded tq3 and some servo strechers....all that should give you a good start, i prolly left something big out but hey I've been at the bar leave me alone lol...oh and a body...and battery, go lipo!!!
remember if you need any help man, shoot me a pm.