dont think there is a gen 3 8, if gen 1 or 2, go with a lss1 or lss2 for side and down scan at the console, the hdi on the trolling motor, If dont have the structure scan box, you will be limited to regular sonar transducers.
The proper transom mount sonar(83/200) transducer for the HDS-8 is an HST-WSBL; if you want to use a shoot thru the hull transducer it would be PD-WBL; both are around $65. The ease in installing a shoot thru the hull transducer is directly proportional to the ease in access to the hull at the transom. Dont remember how a Bumble Bee is set up as far as gas tank and battery placement.