Kerry,
It sounds like whatever cam you have in your 250, you aren't too happy with it. As far as a recommendation for a different cam that would give you more vacuum, take a look at the Comp Cams website. I think their 260H cam and kit would probably do about what you want for a street engine. Cam specs are: powerband - 1000 to 5000 rpm, advertised duration 260 degrees (212 degrees @ .050 lift), .489 lift with 1.75:1 ratio rocker arms, and 110 degrees lobe separation. The also make a 268 degree cam which gives you more power, but you lose some of the vacuum. Check out their website at
http://www.compcams.com and take a look at their online catalog. They also have springs, lifters and timing gears to go with the cam.
