Purchase advise
matching numbers, matching numbers, matching numbers... Bah Humbug!!! There are plenty of buyers out there that don't give a whit about matching numbers. They want a cool car that is fun to drive and turns heads. I get publications that list sales of cars with detailed descriptions from the big auction houses. Many times these days resto-modded cars are fetching as much or more than their bone stock counterparts. Sure there is value in a reference car and actual numbers matching cars could have some extra worth if they were a particularly sought after car, but that doesn't mean that there aren't lots of folks that would love to have a car with minor modifications like yours. I'd rather have a 1970 340 than a 1973 340 all day long. There's no way to predict what that car, well maintained, might bring in 6 or 10 years, just like there's no way to tell if the bottom might fall out of the real estate market or the stock you hold. Like living in a great house brings rewards every day even if you never see it get sold, having a nice functioning muscle car can too.
Just to stir the pot... it used to be that a numbers matching car was an indication of how new and reliable the car was in terms of all it's mechanical systems. By now I would bet that 90% of numbers matching cars have had their engine and trans pulled and rebuilt, just like most of their other mechanical systems, Even if they only have low miles on the clock. I think in reality matching numbers is a long outdated measure of a cars originality or reliability.