I had the experience of building up a 1987 Gardin from my youth using same era Shimano 105 groupset. I thought it was a good experience for me. The parts were purchased used locally and through eBay. In the end the project cost more than what I anticipated. I couldn't even recupe my cost if I were to sell it today, but the emotional value it carries is priceless.
The confidence I gained from that build allowed me to do two more conversions.