I would love to see a picture of your new asset. I sounds like a nice addition to your collection.
I shoot a 465 grain conical out of a 45 with 75 Grains of 3F. It's very accurate. My guess is the higher charges may work but will not be necessary.
I have been told but never verified that rifles will often have two sweet spots, one down low at 65-75 and then another up high in the 90-100 range. This big bullets really kick at the higher charges.
Have fun and post a pic.