They appear to be nuclear reactor modules, telescoped away from the rest of the station and each other for safety purposes.
I googled 'MSFC-70-PD-4000-53' and found NASA's 1970 Space Flight Evolution proposal, which describes (among other dream projects) a broadly similar "space base" design, albeit more general purpose than the fuel depot:
The space base will serve as a focal point for a wide variety of orbital activities taking place in low earth orbit. It provides continuous support services for permanently docked experiment modules, control/monitor functions for detached experiment modules, and periodic refurbishment/resupply services for these modules.
Docking, servicing, and recharging functions are also provided to the space tug which was utilized in the initial assembly/buildup of the base and which now provides a variety of support functions as a part of the overall base operations. Included are such tug functions as overall base exterior inspection and repair; service of the nuclear power supply; support in the unloading of upcoming cargo from the space shuttle to the base; service, inspection and retrieval of remote experiment modules or satellites; and transfer of crew and cargo modules from the space shuttle to a nuclear shuttle for missions to lunar and geosynchronous orbits.
Versatile docking facilities are provided for the space shuttle at the base to enable accommodation of frequent crew and cargo deliveries. During use of the space shuttle to resupply the nearby propellant storage depot, the base will monitor, support, and provide shuttle crew accommodations if needed. Monitoring of propellant transfer operations, servicing, and maintenance at the propellant depot will be provided by the space base/space tug system.
Another NASA document, Space Base Preliminary Nuclear Safety Analysis, calls the 'bunny ears' out specifically as (nuclear) reactor power modules.