What to expect out of mild build 360

I installed flat top pistons to raise my compression on a 360 /after getting everything together and installed they were .060 farther down the hole then stock dished ones ,they were 0.120 down. they were adv, to raise compression but they lied/so flat top pistons doesn't mean anything . but with the 268 cam installed I had 140 psi compression and with open chamber heads .this was in a 3/4 ton pick up with 3.55 gears /stock trans and converter/ tires were 9.50 #16'' and it had no problem moving out or pulling a heavy load but I could get it to ping ,I would check your tune up and don't go over 35 deg on timing. also your spark plugs are too hot IMO 12 champion heat range would be better/ 14 are for 318/273