Jon:
By any chance; are the new lifters Comp Cams??? The reason I ask, is that I had the same problem during the summer. A long with a half dozen other guys I know. It turns out that Comp Cams had an issue with packaging and they shipped (through distributors) a ton of lifters that were labeled wrong. The ones they shipped were for 460's and not FE's. Unfortunately, they fit in the lifter bores but they work (terribly), so users don't recognize the problem immediately. The
oil hole on the lifter is in line with the
oil pump channel and you get a direct shot of
oil pressure from the pump into the lifter (hole needs to be perpendicular). It creates big-time crankcase pressure and will blow smoke and oil out the breathers. It also fills the valve covers with oil before it can drain back into the crank case. I couldn't figure it out and kept changing the restrictors in the galley trying to compensate for it. When I finally figured it out and called Comp Cams; they admitted they knew about the problem and they would send me the right ones next week. I told them to stick it up their bottom and they better have them here, FEDEX next day (which they finally agreed too). What they should have done was sent out a notice or do a "recall", so that guys like us would know to check. Unfortunately, that's admitting a mistake. Another guy here in Jersey spun a bearing and blew a hole in the motor because of it. This would apply to through pushrod oiling. I only mention it because the sympton you mention is analagous to this issue also.
Bernie