RPM at 70MPH

Since this is turning into a question and answer about cruise RPM @ 70MPH, I'll throw out my combination that I hope to have running this coming spring:

1971 Duster, figure 3500LBS with me, a full tank of gas and spare tire
3.73 8 3/4" with 285/35-18's
6.1 with ported heads that flow 348cfm @ .600", TTI headers
.219"/.223" @ .050 .571"/.574" @ 112comp cam
.70 5-speed overdrive

I'm hoping this gives me all day freeway cruising @ 70-75MPH. What do you think?