Aftermarket gears?

Asking seriously, why does a crappy clutch lead to a 3rd gear issue? Reason i ask is I am running a clutch I should not be, the mcleod street pro with a 440 and A833. I would rather replace the clutch over winter instead of trans gears if i am flirting with danger
I'm told I have a "crappy" clutch but it hits like I'm getting hit by a freight train. I only destroyed 3rd gear because I had 2 passengers in the car that weren't exactly small. I'm going to leave the clutch and PP as is and build up the tranny (hence why I asked if they make stronger gears) but still waiting for answers on that.