You can calculate if those turbos are going to work rather easily, if not too precisely.
Two simple ways to do this.
Donor engine rated Hp
divided by the number of turbos on it.
multiplied by the number of turbos you will run
equals the estimated Hp you will support.
donor motor rated at 280 Hp
divided by 1 turbo equals 280 Hp
times the number of turbos you will run (2)
equals 560 Hp
this is assuming that the fuel types in both engines are the same (gasoline to gasoline or diesel to diesel).. not that you can't use a diesel turbo on a gas engine, just that this method leave a little to be desired.
a slightly more accurate way if you are mixing and matching is:
Donor motor one size, 2.0 liter times Redline RPM (6000 rpm?) = 12,000
divided by the number of turbos (1) = 12,000
Receiver motor size, 5.0 liter times redline rpm (5000 rpm) = 25,000
divided by the number of turbos (2) = 12,500
12,000/12,500 = .96 or 96% chance of being correctly sized.
keep in mind that this is assuming your target boost pressure is approx the same for the receiver as what the donor motor was expected to handle.
and is a very rough way of determining if the turbo will work. If both of these calculation say the turbos will work, they will work. they may not be the best fit but they will fit and make the horsepower that step one says +/- your engines efficiency vs the donor motors efficiency.