Vacuum diagram for 78 chevy c10 pu 250 inline 6

google for it
or buy paper bound Service manual. off ebay used and rare !
vacuum varies by if car is calif or federal car. USA< or export model.
3 kinds for 3 kinds of smog laws 1979
sorry there is no other ways.
Chevy has no answer now. this old .
the online manual
shows 6 vacuum maps for one 250 engine
for cal/fed ,and light and medium duty ratings
sadly will not zoom and be clear
the online jokers scan a real book and messed it all up.
no digital books then so must be scanned, and correctly .

See if the diagrams in the link help

https://www.gmsquarebody.com/threads/85-c10-vacuum-hose-diagram-pics.29486/

https://www.google.com/search?q=1984+Chevy+C10+vacuum+hose+diagram

..

https://www.autozone.com/repairguides/GM-Full-Size-Trucks-1970-1979-Repair-Guide/VACUUM-DIAGRAMS/VACUUM-DIAGRAMS/_/P-0996b43f80cb0d10

is the truck c or k 10--20-30 --we dont have manuals and online searches have only ever poped up a supplement repair manual for sale this link is on site that sells it -ebay --amazon--and others
1965 Chevy Pickup Truck Repair Shop Manual Original this is some of the specs for a c10 and they came with a 230 inline 6

1965 Chevrolet C10 Truck Factory Specs eHow Chevrolet Wikipedia and this is specs for the first gen c/k

Could be a 194,230 or a 250 six cylinder engine.

You have to buy it. Look to a library first.

do you have spark? Do youi have fuel? uf you have both timing is off on wires.

didnt specify much like engine size--generic answer--67 carbed vehicles used a simple cable to linkage hook up on side of carb
1968 Chevy C10 Inline 6 250 Carb upgrade Install Holley 350 CFM 2 barrel... and if you have bad slap engine may not make it to far before blowing up or seizing

all inline 6 cylinders 1 5 3 6 2 4

Use a industrial vacume tester, check each port coming off of the manifold, run your lines.