Going great guns there. Won't be long!
After the Rover engine experiences and popping driveshafts, when fitting this engine, wanted to make the driveshafts as straight as possible. Also the engine angle as near as the donor. Had lots of problems with popping driveshafts even with the engine at a "tipped" angle. Tried different models of Rover driveshafts. Ended up, Marlin had changed the engine mounts that fixed the problem.
But if Marlin are using these exact mounts for racing and had no problems while racing (oil pressure problems or drive shafts popping), then I would guess you should be ok.
Here is mine engine angle as a comparison.