I just rebuilding the carbs on my 72 z (car sat for 30 years), but now, I cant' get it to rev over 4000 RPM's. It won't free rev or while I am driving. It idles fine, but it is lacking the power it should have. I tried reseeting the float levels, made sure the lines and clear. When I try lifting the barrels, the front one almost stalls, the rear has no effect. When I place the flow meter over each carb, the fron one gives a good reading, but the back one makes the engine rev higher. This tells me that the rar carb is running lean, but I can't get it to increase the gas flow. Any advice?

Sounds like you need to set up your carbs right. Go through the procedure in the FSM, Haynes, or ZTherapy video. They'll all get you close.

Hard to diagnose someone else's work on unknown quality carbs from 2000 miles away so will only offer up that a thorough check out of the distributor might be in order...... I know we've had many comments about how our TUNE-UP dvd has solved many a "carb" problem.....

I'd be looking at the ignition timing and advance unit.