Hello, I have a 66 Fastback in good shape, no rust California car, with matching numbers. It's a 302 (upgraded from the original 289) with manual transmission. It was my younger brother's car and he passed away 20 years ago and I'll never sell the car. But it would be far more fun to drive if it had a manual transmission vs the automatic. Does switching the tranny devalue the car? (I will keep the original one with matching numbers for the future).
Curious what the opinion is on this. I...

Transmission conversion 66 fastback - Devalue car?