The new bridge base has to be carved to fit the top. It's made to fit a 500/1 top, which is more curved due to the small body. The Senator is less curved there. So as is, the bridge base only touches the body at two points, on either side. This needs to be fixed. This whole thing is not going to be cheap, I'm afraid.
And then the bass will need fret leveling/redress. Still no verdict on the pickup.