Maybe lay one over the other and see what's the same, what's close and what isn't even close. Tweak the new one to be as close to the old one as possible. Someone good at working with sheet metal could make the new one look and fit like the old original sample having the same dimensions and contours. If you could borrow someones good/original '36 transmission cover, you could do the same type of overlay procedure and make yours into one just like the original sample pattern. Also, keep an eye out here and on eBay. If you find a deal on a nice '36 trans. cover jump on it and sell your old one to someone who likes the challenge of reworking sheet metal.