It looks like you're rocking a transverse fwd set up right now. There's not a lot of hope of stuffing a V10 in there unless you turn your car into a tube frame car. Sounds like you have a nice spec v70. If it's in decent shape and you sell it then you can put up the funds for a rwd Volvo variant. That will give you a much easier, better set up platform for a rwd V10/12. I'd recommend a truck V10 as they seem most available. A Ford truck triton V10 can be had in fullsize pickups as well as some buses. A dodge ram V10 can be had in full size trucks as well. You're v12 options are really limited to Jags or a Toyota.

Edit: bmw v12 as well