Steve, I never knew this about bronze bushings and had always used grease before installing the ZF. Do you have a technical bulletin or article confirming that grease prevents the bushing from lubricating properly?
No offense intended, I have simply never read or heard this before and I have read many books and mag articles on engine rebuilding.
I have gone back to using pilot bearings and don't use bushings anymore. I believe bushings are less tolerant of the potential misalignment of the shaft in the bearing due to offsets created by line-boring the crank and other manufacturing variances causing a shift in the crank centerline.