I would get a timing light for sure. I once put in a cam 4 degrees off in a 350 when I was a teenager and it ran great, until you tried to go over 4000 RPMs.
. I didn't have a timing light then either and just eyeballed the rotor. So double check your on #1 TDC, ensure the rotor is lined up with #1 plug wire and then set your initial timing which is probably anywhere from 4-8 BTDC degrees on that engine.