[racer]

A same year 356 motor will hold value better than a 1967 motor imho. The most valuable motor is the one the car came with from the factory.

A "numbers matching" car is one that has the same chassis, engine and trans numbers as installed at the factory. Everything else, while "period correct" is non-matching.

In the end, the "value" will be placed not by you, but by the buyer and his/her intended goals. Someone may not care at all as long as the car runs. Others might want a matching numbers car. Others still, given the rarity of numbers matching, would next prefer a "correct year" motor.