750 uses the 6 burner manifold with separate oil reservoir. The newer 750 and the 1000 has the 12 burner manifold with oil mixed fuel, the new starting motor and a auto-start ECU. Before RAM closed, they were experimenting with a bigger compressor to provide more thrust. That's why some of 750s and 1000s have different compressor wheels, but the same turbine wheel.

FYI- JetCat, AMT, RAM and Simjet all use the same parts from the same people. The only difference is the outer shell.