Not that I know of. But don't let that stop you from making your own ;)
Hmm, don't have TechManual and haven't made a Mech in over a decade, maybe more.
Let's do this.
*Grabs 1992 book*
OK so to make a Tomahawky style Warhammer I need:
Large cannons on either side:
2 * AC 10's
I need LRM racks in each torso. The models have 12 missiles, so let's say LRM10's
2 * LRM 10's
Tomahawks have 2 machine guns in the head, but we only have 1 BTech crit slot. 2 smaller linked Machineguns in fluff can be represented by the stats for 1 Machinegun in BTech. Using the same logic, the gun clusters in each torso can be a flamer and machine gun in each cluster.
3 * Machine Guns
2 * Flamers
And finally the SRM 6
1 * SRM6
That is like 26 tons of weapons, way more than a classic Whammy. Plus 5 tons ammo (1 ton LRM, 1 ton SRM, 1 ton MG and 2 Tons AC). Now the Tomahawk noted as slow and maneuverable, so I can justify a smaller 210 engine, but I'm going to have to sacrifice armour or heat-sinks. Heat-sinks it is.
So with 70 tons to play with:
7 for Internal Structure
3 Cockpit
3 Gyro
9 Engine
14 Armour
26 Weapons
5 Ammo
leaves 3 for heat sinks.
So 13 heat. The flamers and LRMs won't be firing at the same target anyway, so 2 * AC/10 + 2 LRM/10 and SRM/6 equals 18 heat. [blank] (my 4yr old son insisted I add the smiley)
That doesn't seem ideal, but it looks like a close match for the Tomahawk and might be a bit of fun before an ammo explosion obliterates it.
Have I missed anything?