had the same issue with mine. tried the starter shield, but that was a waste of money.
Installed a new starter from a mid-late 90's 5.7, bolted right up and now it starts like a new truck, always.
__________________
Greg
1974 GMC
1/2 Ton SWB Fleetside
L33 5.3/4l65e
.................__
............._____l __\__
..............l_(O)_ l___(O)]