A synthetic call involves Long Stock & Long Put, so I'll assume you meant Synthetic Long, Long Calls and short Puts. Using the 85 calls and the 75 put would be a Synthetic Long with split strikes.
Sorry, my bad. I meant to say equivalent not synthetic.
The long 75/80 call spread is equivalent to short 80/75p spread that you did so if you do the former instead, your entire psoition becomes a long 75/85 call spread (10x).
