As for not degreeing the cam, that is done a lot. The possible issue is that the cam can be a few degrees off one way or another; sprockets and keyways can be machined in error, and cams can be manufactured in error. Degreeing the cam is a process that requires tools: a degree wheel and dial indicator.
A cam being off 3 degrees will indeed change the engine response in a measurable way. Degreeing the cam is the right and best way to do it, but it takes the tools and time and so its understandable why some don't bother. In this case (ASSUMING the old cam was indeed around 285 degrees duration), the engine change is already going to be pretty dramatic even if the cam is off 2-3 degrees.
You probably dont have to degree it but to roughly verify line up the timing marks as best to straight as possible, put in both i&e lifters put a straight edge across the top of bot lifters.The intake lifter should be around .010 to .020 higher than the exh lifter when the valves are on overlap that should be 2-4 degrees advanced.
This is a way to at least say that the cam chain is on the right tooth. It eliminates the chance that the cam is 15 degrees or more off, but does not show that it is 3 degrees off.
