What diameter flywheel does this bellhousing take

The '78-'81 truck catalog shows part #3893729 as fitting '78-'80 A-B-D-W-CB models with 318/360 and 11" clutch--1 digit off your casting number, which isn't uncommon.

The same application uses flywheel #2843211, which cross-references to ATP #Z368, LUK #LFW106, and Pioneer #FW326, all of which are 11", 143-tooth flywheels.