Also depends on outside temperature, ......in Texas in Augusts I was running 200-205 after several fixes...when I bought it it was running 230-235, (straight aways 230 ,ea uphill it would climb to 235 and I was praying for lat ground)...but in non summer times, around 180 (after the fixes)
You say its a 400 do you have the 'fillers"...the masticated (now rubber) ones on either side of the bottom of the radiator? Those accounted for 5-10 F on mine (mine were missing at purchase)...also, do you have the bottom metal filler? (I did when I bought mine) and lastly is it an AC car? all 400s and AC cars had those fillers .
PO had also installed a pusher helper fan that I removed , it was blocking more air than it helped.
what about the water pump?
https://firstgenfirebird.org/forums/ubbthreads.php?ubb=showflat&Number=107803&gonew=1#UNREAD