New crate 454

This is a very different post from most 454 overheating issues. Most have older MH's with old radiators and components. Yours is all new. My thoughts are that this is something simple with the install. Maybe as Sum1 says it just needs time to break in. I have had gone through 3 thermostats because of overheating. Right out of the box they would not open up all the way in boiling water. Does it open up about 3/8 ins? Also is it installed correctly, I have made this mistake in the past and installed it upside down. Is the tube dia from the old radiator to the new the same size or larger? When you installed the new eng was the temp sensor in the left hand head a new OEM sensor? I found a 20 degree higher temp reading from an aftermarket sensor. When you set the timing was it from the top of the eng or the bottom? If from the bottom I believe you use no. 5 plug not no. 1 with the tan wire from the distributor disconnected. When you rev the eng do you see at least 20 degrees of advance? I have advanced mine from 4 degrees BTDC to 9 degrees without pinging on reg gas. It did not make that much difference in cooling but made a difference in power(reduced 40-60 mph times from 14 secs to 12 secs) which translated to better hill climbs, about .25 mpg increase and quieter running eng( less header noise). So to me it is well worth doing but I don't think it has caused your overheating condition. If none of the simple checks works I would use an IR gun across the radiator and take readings from top to bottom and look for cold spots( indicating a blockage) and a least a 50 degree delta T from top to bottom. Hope you find the problem. Let us know how you making out.