rebuild or crate
Personally I would rebuild but first thing I would do is go to a local salvage yard and buy a used but running 350 or 305 check around for the cheapest price. Install it in your 55 and enjoy it while you rebuild the 327. This way you can take your time on the rebuild. Also if you buy a 350 with vortec heads you could put them and the intake on the 327 too.
Then when the 327 is done you simply put the 305/350 in craigslist and get the money back. There is always looking for V8 chevy engines.