No Volvo expert here but from the threads I've read and many of the with DonS in the mix, the Volvo is a good drive but a PITA to find info on. I have found many items for the drive area but no full kit.
Volvo parts are easiest to find using the engine model number. Sorry but I don't know what a seal plate is. Are you talking about the seal around the backside of the transom shield?