The MK103 gunpod as seen above are of the first version, IIRC it's a picture of one of the A5 prototypes fitted with this armament. The A8/R3 indeed carried similar pods but they were slightly different, more streamlined. Other aircraft carried the 103, some versions of the Bf 110 could carry a belly MK103 pod for example.
Due to the high recoil of the MK103 precision was not very good for the wing ounted gondolas, moreover the performance loss incured by those were quite large, making the aircraft a sitting duck.