I'm not an ork player myself but my regular opponent is so ill do my best.
I'd suggest boyz. Lots and lots of boyz. A ten man squad can dish out in the region of forty attacks on the charge and I haven't even added the Nob into that calculation, personally I wouldn't bother with trukks and up the squad to twenty with sluggas and choppas. Trukks are just too fragile and the boyz only have a 6+ save so you need as many as possible to soak up firepower and keep their leadership up. If you take a warboss your nobz count as troops choices for objectives purposes, sticking a nob squad with your boss and a mix of klaws and big choppas works for my regular opponent. Burna boys are good too, multiple flamethrowers that count as power weapons in close combat. Win.
Whether or not you want any heavy weapons is up to you, just bear in mind Orks are famous for not being able to hit the broad side of a starship, never mind a barn. The loss of the extra attack for the boy carrying it just isn't enough off a trade off for me.
If your opponent has tanks tankbustas are handy, also a power klaw on your nobs is always a good idea. The only other useful thing I can think off for that is a weapons battery with zzzap guns.
All that being said, a mechanised force in Trukks and battlewagons is fast and hard hitting, I'd suggest that for opponents who don't have an over abundance of firepower. For tau and guard you're best off with numbers to soak up the stupid amount of incoming fire until you can mince them up close.
That's the best I've got I'm afraid, hope it helps.
Drink deep from the chalice of victory, and remember the fallen.