Well, the original engine would make the car worth more, but since you don't have that, it really doesn't matter what you do, as long as it's what YOU want to do.
I personally LOVE the 327. I think it's probably the best designed engine Chevrolet ever came up with. A well built 327 is a screamer. It was available with horse power ratings from 210 (Camaro) to 375 (Corvette).
I've had several cars with 327's in them and you really can't beat it for power, reliability and even mileage if you keep your foot out of it!