Not cheap, but worth it.
Hi, I did my 27 a few years ago, and it was about $250. I had it done at http://www.neprop.com Here's the shaft info http://www.aquamet.com/default.cfmI put a pss shaftseal in at the same time, and a flex coupler.http://www.pyiinc.com/I'll do it all again on my newly acquired '86 30.Good luck, Kevin