I see a carriage bolt being pointed-to in the 1947-1955 1st series Factory Assembly Manual diagram (Section 6, Sheet 12.00) - 3701135 BOLT

Group 0.002 BOLT - NUT - SPRING - SPACER, Engine Mounting
1937-1954 COMM., UTIL - frt. mtg. (3/8 x 24 x 1 1/2" drld., carr. hd) - 3701135 (part number shown in Factory Assembly Manual)
(3/8" diameter, x 24 tpi, x 1.5" long, drilled carriage bolt - drilled for lock pin, I guess)


Also,
- the circled-instruction/illustration 2 is referring to the bolts/nuts that comes from the factory with the plate (here are photos of a factory replacement plate/bolts/nuts - the bolts are not drilled for a lock pin)
- the circled-instruction/illustration 3 is referring to the bolt in one of the rear motor mounts (insert illustration at upper right).
"It only says they are furnished by the Engine Plant, tighten to 55-75 ft lbs and bend the lock ear to lock the bolt."

Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.