bone head move/ few questions

Ok some of you might get a laugh out of this one.. I changed my oil and filter late evening before a fishing trip. Next morning on my way out i noticed oil pressure drop off and saw my bilge flooded with oil. I shut her down and got towed in. The old oil filter gasket stayed on the engine and I didn't see it and I spun the new filter on so I had a double gasket. Engine ran fine after I have probably put 30hr on since. Last few trips out my Engine has been running ruff a few minutes after start up then it is fine. At 3200 im hearing noise coming from engine it sounds like chatter or maybe pinging? Also last trip out i think i heard noise from engine and slowed down and heard what a thought a few small backfires from carb and i had 8 people on my boat. Engine Cold starts instantly and I have a new holly carb on it i been running a few months now. Since I rebuilt the 351 over a year ago I have never put a timing light on it since I didn't have a timing pointer or havn't been able to find one. I timed it by sound which I know isn't good enough. I just wanted some thoughts on all this. Im pretty sure my timing might be to advanced. Does anyone know where I can get a timing pointer? Do I turn distributor counter clockwise to retard timing?