I am afraid not.
A 60 ton Clan chassis has enough tonnage available, (assuming it moves 1/2/0, has no armour, and utilizes an XL engine with endosteel internals) but lacks the internal critical space necessary to actually fit all of that. (Staring at the design right now in solaris skunkwerks
Two LBX20's and 4 cStreak6's are pretty hefty firepower though. Even for a Clan heavy. Also, 12 tons of ammo? That is enough for 45 turns of non-stop firing, most matches do not even last 16!
Now, I *could* build a custom mech from scratch that fits some of that, but I decided a better choice would be to take ye old venerable Mad Dog (Vulture for you Freebirths) chassis and rig it with the LBX autocannons, though I was worried it would not fit them AND the ammo. Thankfully, the Mad Dog's design principle follows the 'fuck armor, put more guns on it' school of thought.
I yanked the dual large pulse lasers and LRM20's from the prime variant, and jacked the heatsinks down to the base 12 (It is in no danger of overheating with just these autocannons). This gave me 28 tons to work with. 24 tons for the two LBX20's, and then 4 tons for the ammo. It is not the loadout I would personally take into battle with a Mad Dog, considering its armour, but for a daring young Trueborn out to claim a bloodname, I do not think it is bad.
A 5/8/0 movement curve (reaching ~80kph at a run), enough ammo to fire the autocannons for about 10 turns (1.7 minutes) before running dry, and just enough armour to keep you mostly intact as you close into range. At 1610 battle value (2222 BV with a 3/4 standard Clan Pilot) it is actually pretty dangerous for the price.
I also made sure to mix the ammo types - 2 tons cluster and 2 tons slug so that you get your holepunching and sandblasting ability all in one. Additionally, I removed the upper arm actuators to clear out some of the internal crit space in the arms. So not only does the LBX20 assembly manage to fit in just the arm itself, but since it is entirely in the arm and the upper arm actuator has been removed, the arms themselves can completely flip around, making this design even more dangerous in a close quarters fight as you maneuver through a formation and fire *backwards* (Hopefully at the rear armour of your enemy.)
The significant downside to this design is the staying power. Light on armour (But then, all Mad Dog's are) and light on ammo. Once you run dry, there are no backup energy weapons, so you will be left adopting dezgra freebirth tactics like kicking your opponent to death. (*spit*)
Additionally, the design lacks anything to absorb hits in the torso. Any breach of the armour that scores a critical hit is going to either blow out an ammo bin and cripple the mech, or damage the fusion reactor. (Granted, a damaged fusion reactor on this design is not so bad - thanks to the low heat output of the cannons. Even with half the reactor shielding gone, this mech is still going to run cool.)