Thanks Pishta. I've been pondering your drawing. The oil gallery is about .600" down the lifter boss so the gallery is exposed to the cut out any time the lifter isn't riding on the lobe and at that point some oil must slosh around the lifter body. I've looked at a standard factory cam which measures a base circle of 1.34, a Racer Brown ST21 with a base circle of 1.21 and a Lunati hyd Voo Doo at 1.19". I also measured a standard hyd lifter at 1.89 and a Rhoads lifter at 1.89".
So we have a maximum difference of .060" lifter height between the generic hyd and 273 Dumbells - big deal. The maximum difference between the smallest base circle (the Voodoo) and the dumb bell lifter height is around .150" so really it should work. The next step is to buy the Comp Cams Magnum 20-248-4 solid cam and a dumb bell and physically have a look. If the lifter doesn't allow the oil gallery to be exposed and it sits a little deeper the the lifter boss that will also help with the push rod angle.
Cheers
