If you are not running a show car, no need to worry about loss of value. Most driver quality Buicks of the end of the I-8 era don't have a lot of value to start with, and a 12 Volt conversion is not likely to do any harm. I seriously considered a 12 volt conversion for my '51, but ended up using a slightly taller 6 volt battery sized for smaller IH tractors from the late 40s and early 50s (IH Series H and M, and likely others) They are readily available in farming country. My only regret is that I cannot find a 6 volt electric warmer to pull off the choke for winter driving. (The car takes forever to warm the carb up from zero degrees relying on the exhaust heat.)