I believe I'll try that. I worked at a logging machinery place in 79 & 80 And was sent to fix a Detroit diesel in a skidder that would run for a few minutes and die. I finally ran a temporary fuel line and it ran. Come to find out there was a shop towel on the pick up tube. The guy called back the next day with the same problem, we told him to check the tank again and he found 3 more towels. When we had the skidder in the shop it had no fuel cap and people would stuff a rag in it, apparently it got several stuffed in it. But you're right it acted like my truck does.
I also had to take off my starter today, I thought it would be like the one you asked about on your 64 C-60. Mine is still different, it has 2 mount bolts to the bell housing. The snout of the starter is square (kinda) and the bolts are diagonal from each other.

'65 C-10, 65 L-60, 65 C-80, 72 C-60 & and a bunch of old Chevy cars.
Never time to do it right, always time to do it over.