23' inboard cruise speeds?

[TunaMeltdown]

As some of you know I became the proud owner of a 1976 23' inboard last November. After hours of custumizing and some other minor maintenance, I was finally able to get out fishing yesterday. My question is, what should I be seeing for a cruise speed/rpm? The engine is a 2006 Marine power 350-330hp. the boat yesterday seemed to like 2200-2500 rpm and we were making 19.5-23 knots? I have been told that the cruise for that engine should be a bit faster and the rpm's higher like 3200-3500rpm? Any suggestions?
Oh yeah and running it at thathose speeds and rpm's I was able to run a total of about 50-60 miles and burn about 34 gallons.