A-518 and 46RH find

1 will be for my 68 Barracuda with a mild 360 ( 360 hp ) and the other is for my 78 Dodge RV C-Class with a 440 and 4.10s.
Which one is best for each application ?
I bought this converter for the 46rh I am building to put in my Travco MH behind a 440.

https://www.transtar1.com/products/...-Ram-46RE-46RH-Heavy-Duty-Converter-with-Bill