I seem to remember the shop price for straightening and bushing 16 lifter bores at about $800. Most commonly used is the BHJ Lifter-Tru. Here's the page out of the BHJ catalog:http://www.bhjproducts.com/bhj_downloads/catalog/lo_res/BHJ_08Catalog_p10-11.pdf
The sleeve is 1.000" OD May not be a lot of support for the bores. I guess it depends a lot on the aggressiveness of the cam lobes.
Not all Oldsmobiles had 0.921 lifters, in actuality the majority have 0.842 Chevy diameter. The conundrum for Olds guys is there were also two lifter bank angles, 39 and 45 degrees. That makes four combinations and I believe Olds used three of them.
If you really want to get tricky the Olds hydraulic roller lifters used in their Diesel car engines used the 0.921 diameter.
I think the only way to cut the lifter diameter would be by grinding.
Bottom line - if the OS lifters are available buy them. If they're not available, get a different block.