I'm no expert, but I have grown lemon Walker, lemon og Kush, Florida lemons, 60 day lemon, SLH, Franco's Lemon cheese, and there is one more I can't think of that was a lemon.
I don't know anything about crossing or breeding but I would start with Lemon OG Kush if trying to get the limonene terp. Super lemon Haze would be next. This just my anecdotal experience. I had a pretty good SLH pheno but still nothing touched the lemon OG. The smoke is good but not as good as SLH. I'm bout to pop some Florida lemons. I strongly recommend it. It is just the perfect hybrid IMO. It isn't a huge producer or anything just makes me the happiest and smokes the smoothest.