Printing problems on Windows XP

Upgraded Windows98 computer w/ new Dell & Windows XP Professional. Everything went relatively smooth but one application using Timberline software printing to an Okidata 393 Plus impact printer. (Old but very good impact printer) Page size has tobe set for check printing but printing slower and fonts not same size as on 98. Tried changing font size, new driver with XP, & Okidata & Epsion. Vendor no help (does not support XP etc.) Microsoft says I have the current driver & Okidata same. Timberline says that same problem exist in W2K but no solution (if you can believe that).