If I were to tell you what I think (thought?) of you, I'd be sacked from my job
Cool BreezeIn the first sentence the use of a present tense (think) emphasises what your opinion is now. The past tense (thought) refers to the past; your opinion may have changed by now.
Hmmm.
To me, in this type of construction, "thought" does not have to refer to the past. It can do, but, for me it can (and very often does) mean that you think it right now.
Addition: If I wanted to indicate what I had thought in the past, I would say "If I were to tell you what I used to think about you..."