I think the relatively low hours (from 1300 - 1850), had a lot to do with my 3400 good experience.
Mine was 3 cyl. gas also.
I did rebuild the carb., and change to electronic ignition, but I had no other issues similar to yours.
I did do a nice job complete repaint.
The beauty for me was that it was a TLB ( I never used the 3pt .)!
1970 Ford 3400 TLB with 1300 hours.
Paid $10,000 in 1986, and sold in 2019 for $9,000.
Bought the L48 TLB with 251 hrs., 3rd function, and hyd. thumb, from orig. owner, for $32K