140 gallon semi cichlid tank stocking

[Cole101]

I'm getting an aquarium in the next few days that is going to be about 140 gallons! The dimensions are 180x50x60cm. Might have to remeasure the height though. I need some help with stocking ideas. So far I definitely know that I want a Tiger Oscar and I also have heard the firemouth cichlids do well with them. I was thinking of getting these fish as baby's but the man who is selling the fish tank offered to sell me his 20in Clown Knife. Would it be safe to keep these fish and other fish together with a fish of that size or will he be to big for them. Finally was also thinking of a Blue Acara. Featherfin Syno, and a common Pleco. Would love more suggestions on other fish that I could put in here or if this is max stocking.