Is there an easy way to identify an engine that was removed from a 914 as to 1.7, 1.8 or 2.0?

2.0 has 3 stud heads for the intake.

look up the number on the front side of the oil filler neck on the case.

Only Porsche 2.0 has the 3 stud head to manifold arrangement.
1.8 does not have head vents.

if you know the year 914 it came from and IF it was the original engine
1.7 4 stud intake w/ d-jet
1.8 4 stud intake w/ l-jet
2.0 3 stud intake w/ d-jet
70-73(?) 1.7 or 2.0
74-76 1.8 or 2.0

disclaimer: no sure about years/engines timeline

Get the engine number and look it up. At least you can see what it started life as...