There was extensive discussion of this before the forums were lost; I guess if you get one of those 68060-in-a-68040-socket adaptors and put a 68060 in an LC630, you can get at least a grey-screen from it.
The adaptors are here: http://www.emulation.com/catalog/off-the-shelf_solutions/production-test_adapters/upgrade_motorola/
...not that anybody is going to pay nearly $500 to swap a 68060 into the LC630