The resulting car would be similar to the car Volvo could have produced if it had continued to develop the 1800 with a version of its DOHC rally head on the B20. Being the same size and weight as the B20, it would not upset the balance of the car and would not require any body modifications. Sharing a contemporary engine of similar technology and design, it would compete favorably with numerous modern, popular sports cars. Low mileage used engines are readily available as imports from Japan at very reasonable prices and are widely used in engine swaps. Further, there is a great deal of performance equipment available for them with more being developed almost daily.
Engine swaps are only simple in concept, never in the details.
As the engine swap project progressed, it became clear that it was entirely feasible and would be a really neat project, but it was also getting more complicated and expensive. But you need to multiply its price by probably four to six times by the time it's installed and is running well. With modern engines there is always the question of the electronic engine management system. If you eliminate it in the interests of simplicity and install carbs, you are likely to lose most of the advantages of the modern engine that produced the high HP output. To get the power back you have to make additional modifications, that, while entirely feasible, can be very expensive on a modern DOHC engine.