Abstract: Disclosed are example embodiments of an irrigation system with a plurality of drive tower structures each including a drive beam configured with left and right, right-angle wheel-drive gearbox mounts, each the mount configured with a plurality of bolt holes for attaching a corresponding legacy right-angle wheel-drive gearbox to the mount. The bolt holes being alternatively suitable for attaching a universal inline drive mount adapter, and configured with bolt holes at a first end of the adapter that correspond to bolt holes in the gearbox mounts, each the adapter further configured with bolt holes at a distal end suitable for attaching an inline wheel-drive gearmotor assembly with transfer case.