Neal,
I've read and heard before that it's best to stay away from split duration cam profiles in Weber applications. I don't recall what the exact reasons are, but I'm sure some of the other "Weber" guys can tell you. Then again, I was told "emphatically" that my cam had too much duration to work well with the 48 IDFs....
Engine Specs:
350 CI, 9.8:1, alum "D" port heads 1.94" I, 1.50" E
Hyd Roller Cam Specs:
Crank Dur @ lash point I/E 336 deg
Crank Dur @ .050 lift I/E 235 deg
Max lift w/1.5 rockers I/E .480"
Lobe centerlines 114 deg
Maybe the reason the 48 IDFs work well with my setup is that the chokes are rather small (34mm).
Mike