For an old iron headed muscle car motor 200-210 degrees is max in my opinion.
I prefer 180-190 degrees in my Duster.
1970 FE5 Duster 360/904/3.91's SOLD
1973 TB3 SpaceDuster 340/4spd/4.10's SOLD
Moparless for now but when the opportunity is right I'll have another one.