Help Needed - Running Hot After Heads Replaced

[mark460]

1998 5.7 Rebuilt about 75K miles ago, running great until a few weeks ago, radiator had leak and overheated engine slightly which cracked head. I put in a new radiator, ran cool like normal, but had engine miss due to leaking coolant in head. Had 062 heads, machine shop found me 906 heads, mag checked, valve job, surfaced, etc. Put everything together, temp gauge keeps rising past 210 degrees. Tried bleeding air out system several times, ran with heater on, cracked lines, etc. Pulled thermostat, put in boiling water and it opened. Top hose going into radiator feels hot, but air being blown thru radiator doesn't feel that warm. On another car, I once had an impeller come off a water pump, but the odds of this being the problem, now? Just not too sure about that. Any ideas would be appreciated. Need to get this back on the road.