302 Vibration

I know I'm probably in denial, but I'm trying to alleviate a vibration in my Fastback's engine that comes off idle peaks at about 1800rpm and slowly tapers off through the revs. It does it in neutral and in gear. Can anybody tell me what this might be besides balance problems? This is my set-up:

1972 302 short block
stock crank
stock flat top pistons
Comp cams high energy 268
'91 E-7 heads
Edelbrock Performer intake
Holley 4160 600cfm
Borg Warner T-10 4 speed that could use a rebuild

I had vibrration in my 289 that turned out to be a broke ring