LA is just a brand by OS Engines, ive never used an OS LA engine, but alot of people dont like them because of their quality, I never neven seen an LA but someone in another post said that their back plate of the crank case is plastic, which can be broken in a crash. I think ABC stands for Aluminum, Brass, Chrome - aluminum piston and a brass cylinder that is chome plated

(someone correct me if im wrong)

I would suggest a Thunder Tiger GP-42, they dont cost as much arond $50 from Tower Hobbies), and it pulls my 4.5lb trainer around nicely.