Value is an interesting thing. Numbers matching, as close to original as possible seems to increase value in the market. Yet there is the resto-mod scenario that goes away from pure stock to re-engineering cars with modern drivetrain improvements; some of these cars command high dollars on the market. It is obvious you have held onto the car for many years and plan on keeping it forever. If that's the case, then do what pleases you with the car. I grew up in Royal Oak in the 60s and 70s, watching the muscle cars on Friday and Saturday nights in the 60s and getting my 400 bird and joining the fun on Woodward Ave in the 70s. Most folks modified their cars for improved performance. Cragars and headers/duals were probably the most common upgrades. We looked at a car to see what mods from stock were on it; in those days, the more the better! Beautiful bird and a really nice start. Best of luck to you.
Dan