I like the big 1958 Buicks! It is your car, and you can put in it what you like.
As for value, I think to a Buick enthusiast, it is better with a Buick engine, for power, probably a version of the 455, for nostalgia a version of the Nailhead. But if you are after maximum performance for a budget, the Chevrolet motors are hard to resist. A Buick engines cost more! It could be moving to a modern LS type motor is more acceptable than a version of the older small or big block Chevrolet, because Buick engines came to their end of production.
Just my thoughts, but like I said it's your car, build it for yourself, and enjoy it! (that's the number one rule).