While you're at it, fix some of the spelling mistakes and unnecessary 'upon-Tyne' type naming. Try offering the Prussian instead of John Bull. Perhaps the scenario should offer the Prussian (1837) locomotive instead? That would be truly advantageous, because it would carry you through to the American C in 1848. You're right that the John Bull is no gift in 1835.
In the game editor, open map #07BIR~1 (after finding it on your hard drive and backing it up).
