5.2 magnum swap questions

ok, i have a couple questions i am swaping a 5.2 magnum into my 66 valiant.

I installed a la360 oil pan and used the Magnum oil pan gasket.
i also used the la timing cover.
Am i going to have an issue? I read a couple posts where guys have modified the gasket because of leaks... and now i am parinoid.

worst part is the motor is painted and in the car almost ready to fire up.

second part is i have also found guys are having to slot one hole in the Magnum flex plate to bolt up to the convertor.
mine bolted up without issues. is this because most guys are using a 5.9 magnum?

thanks in advance for the help. FABO rocks!