Hmmmmmmmmmmmmm..... It's doable but likely too much effort for the benefit. The reason for twin turbos is usually elimination of lag time. However a large intercooler sutup like the Volvo is already a setback in the lag time fight. A pair of small turbos to do the job of one big one is the key here. It is possible to build a wastegate setup and quick spooling turbo to get the same results though. That is something I have tried and had good sucess with. Don't forget two turbos means two of all the related plumbing. Air, boost, exhaust, coolant, oil feed, and oil drain all must be doubled up. The amount of fabrication would be challenging even to the boys and girls at NASA. A nice supercharger setup, now that keeps me awake at night.