Lower Unit damage.. Keep and Repair or Toss?

I found a used lower unit locally for great price, the stainless prop alone made it worth every penny that the main reason for the purchase. The unit itself though does have some damage on the side fin on one side only (see photo below). How much will this affect operation if I did try to use this one as an emergency/backup spare unit? I did see another one listed that had similar damage to the forward fins where the owner said it did not affect operation but that one also had hydrofoil installed. So I'm not sure if the other seller was either A) Full of crap or B) Installed the hydrofoil to correct any problems the missing sections caused.

I say have it repaired. A good welder can weld a piece in and grind, sand and paint!

Yep x2 for keep it and repair it. I had similar damage from using a hydrofoil for years, plate isnt made to handle the forces… i git a lot of prop cavitation burn until i fixed it