IMHO..a balanced primary and a trued crank is as good as it gets..the "vibration" at idle is the heavy crank/rubber mounts...NOT clutch "wobble"...( balancing the clutch will help, JUST at 1500 rpm theres an inherent shake to the doo 800R/motor mount sytem...touch the throttle and its smooths right out)...BJ
BTW...a "balanced/blue printed" SBC is = "3/4 race cam"...all "catch phrases" for guys who never built/race cars (parking lot posers)...the most recent build (have a few close car buddies from days by gone) is a 1260 HP Rehr Morrison 605 with the best of the best pro stock componants (with spark plugs out you can almost spin motor by hand by rotating balancer) this motor is a free spinning NA monster (7.90s @ 170 in a 67 chevelle)...anyway...at idle its smooth as silk BUT rocks the car... (back in 1990) my '71 Z28 w/468 was balanced, only made 650 hp and idled in gear at 750 rpm (thank you Smokey Yunik)...smooth BUT rocked the car due to the .720" lift roller cam and solid mounts (thats almost a 3/4" race cam...LOL)...I ran 10.90's @ 125 on DOTs/mufflers 20+ years ago...