I picked up this project with the Datsun ZX drivetrain already in place, so my problems are driven by a non-original drivetrain, my ignorance of the Healey and general pains of working with a near 50 year old car.
I assembled the engine/trans complete, carbs, exhaust, alternator, aircleaner...on an engine stand, with the thought of just dropping it in. I ended up removing the alternator, aircleaner, engine mounts....it was just too tight of a squeeze while dropping it down in the bay. I then had the usual issue with bolts, especially on the drive shaft.
So, nothing time didn't solve, but I could tell that the car really didn't want a foreign motor back inside it