SheepShaver crashes when booting Mac OS 8.1? You need the Old World Mac ROM listed separately (see the downloads). Shut down SheepShaver if it's running, then launch the SheepShaverGUI and under the Memory/Misc tab, select that Old World Mac ROM file, then start SheepShaver and it should boot Mac OS 8.1 successfully.
You can use SheepShaver on Mac OS X 10.5/PPC and on Intel Macs. It will run Mac OS up to version 9.0.4. Alternatively you can use the free download version of System 7.5.3 and update it to 7.5.5, or use an original Mac OS installation disc for use with SheepShaver. The only complicated thing is that you need to get a Macintosh ROM for SheepShaver to work.
McKeehan M. 2016. Intellectual Property Rights Issues for Software Emulation: An Interview with Euan Cochrane, Zach Vowell, and Jessica Meyerson. The Signal: Digital Preservation [Internet]. [cited 2016 Feb 19]. Available from: -property-rights-issues-for-software-emulation-an-interview-with-euan-cochrane-zach-vowell-and-jessica-meyerson/ 2b1af7f3a8