I have done this with one of my motors. One of the best resources are the diagrams in the HP book by Steve Christ on How To Rebuild Your Big Block Ford. The diagrams are a little small but they illustrate quite well the
oil routing. You need access to gundrilling technology. One of the more difficult
oil ways to block is the
oil groove behind the #3 cam bearing as the side oiler uses the grooved cam. If you have a block cast as a side oiler and drilled as a top oiler (probably a service block with ribbed side) the bosses etc pretty well tell the story on where to drill. The part to really watch for is the side holes get very close above the main flanges. The other big conversion on oiling is hydraulic back to solid lifters. It's not really difficult you either need to block a hole or drill one right? I have collected quite a bit of info on this and other oiling tips for FE's. If you want more get in touch with me and we'll arrange something.
Cheers Nick