pump is still leaking

I am hoping you guys have an answer for my leaking pump
pump housing is hayward jacuzzi magnum. pump is AO brand 1 HP. it came with my house so i am guessing 10 yrs old
2 yrs ago I changed out the pump housing because of cracks, didn't take apart the diffuser. i noticed on the end of the diffuser there was no gasket. there was an o ring around the seal housing. re assembled it without any leaks

now the motor finally died. I purchased an exact replacement AO motor. that company has been replaced with "century" brand. appears to be exact in every spec. now I have a constant leak at the bottom. i changed out the mechanical seal being meticulous not to touch it, o ring on seal housing. noticed the o ring on the impeller is worn but doesn't match the hayward kit i purchased. same circumference but diff shape.

even put everything back with the old gaskets. tried every combo with gaskets new and old. took it apart 15 times. any advice??