Ticking noise under load?

[cst350]

Just got everything together and on the road. Rebuilt engine, new TH400 trans from Summit. When I jump on the gas I get a ticking noise that sounds like it is coming from the trans area.

I read that sometimes the flexplate can rub the starter under load. I have a GM performance mini starter. The clearance between the pinion and flexplate is .04 (which is the smallest the directions call for). Would be cheap to get the shim kit to increase the clearance... anyone think this is the problem?

I get zero noise when in neutral all the way up to 3500 rpm. Same if I put it in gear and hold the brake. It is a standard bore 350 with cast iron Vortec heads and my timing is set at @8 deg.
Really don't think it is exhaust or valves since there is no noise when not driving.