Welcome to the 'club! The car looks great. The M42 has a bit more torque than the old M10 and a lot of the same high-revving charm, though I'm afraid it doesn't return the same kind of fuel mileage.
Before you put the motor in, be sure to loctite the lower pan bolts & take a good look at the profile gasket. I'd also be tempted to replace many gaskets if I meant to keep the car for a while (especially that pesky oil filter gasket, leaks all the time).