Have a CUCV M1008 Truck with 14,279 miles but has hard time starting (won't start now). The batteries are new but drain fast. Lucky to get 2-3 times. The alternators are rebuilt, new lift pump, new glow plugs. The starter looks original. I'm thinking worn out starter? Prior it would start ok with 15 seconds push button glow plug switch

Second issue is found leaking freeze plug above starter, can the plug be removed and enough clearance for a block heater to be installed or replace plug and put the block heater in other location?