I googled it and couldn't find anything. You could contact the Seller and ask what the image circle is but he sounds like he doesn't know much. You are right that it would be a normal focal length for 8x10. If it covers 11x14 it would be a medium wide or slightly wide lens.
I don't know how low your budget is but I purchased my Fujinon 250mm f/6.7 lens in an accurate Copal shutter off Ebay for a little less than $300.00 including shipping. These come up occasionally on Ebay for around the same price. Just make sure you get the f/6.7 lens because it has plenty of coverage for 8x10 with movements.
I know I'm talking more money but I can bet you this shutter will need a CLA. By the time you are done with it you are approaching the cost of a much better lens in a much better shutter.
Good luck to you!