Hi Moonshadows:
If you cant find a diagram in the manuals, you may take a look at the Autozone website collection of vacuum hose diagrams for the Chevy truck:
https://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528004c3cbAlthough they do not have diagrams for 1981-1983, they do have them for up to 1980 and 1984 onwards. There is a diagram for 1980 that is coded "DT" and shows a 2-barrel carb. If all your emissions stuff is still there, you should be able to compare what you have with the diagrams and figure out what hose goes where.
If your carb is original to your truck, it is probably a Rochester 2SE or E2SE. These carbs were known as the "Varajets" and maybe this is your confusion as to "variable venturi". Yours is most likely the E2SE which has computer controlled metering. There has not been a variable venturi carburetor made in the USA for a street car in a long time, if ever...My last recollection of a variable venturi carb made in USA was for WWII aircraft engine. Variable venturi carbs are common on motorcycle engines, all out racing engines and some older British cars.
Regards,
Henry