What you have there is a Speedmaster motor mount and parts should be available from Bill McGraw at www.rossisales.com .
You should be able to reuse that mount. It can be narrowed or widened by adding or subtracting washers or retapped to make it fit a new engine if the holes are a different pattern. It can be flipped over also.
The aluminum is really hard so be careful if you have to retap the mount.