All Camaro V8 engines used a 3/8" fuel line going from the tank to the pump. (Only the L6 cars had the 5/16" fuel line.)
However, the fuel line going from the pump to the carburetor was different, depending on which engine/carb you had. For your LF7, your car came from the factory with the 5/16" fuel line (original P/N 3932446) going from the pump to the carb.
Your original assembly line fuel pump was P/N 6440524 (type 40503), but was replaced in SERVICE by P/N 6416712 (also type 40503), which was also a 5/16" outlet pump. Then, only after a few months, the 6416712 pump was replaced in SERVICE by P/N 6416886 (type 40524). As far as I can tell, this pump has a 3/8" inlet
AND a 3/8" outlet, so I'm not sure what the dealers did if they had to change a bad fuel pump under warranty on a 67-69 2bbl carb equipped car!! I can't find any notes regarding this so maybe they just used adapters?
Anyway, your May, 1968 LF7 Camaro should have a 3/8" line going from the tank to the pump and a 5/16" line going from the pump to the carb. Finding a replacement for the original assembly line 6440524 (or first version service replacement 6416712) pump, is probably going to be a challenge since all I can see from the vendors is the 3/8" inlet and 3/8" outlet pump, which was originally used on the L30 and L48 engines.
EDIT: After a bit of searching, I found a place that states they have the original 5/16" outlet pump in reproduction. The "Truck and car shop" in Anaheim, CA shows it as their
PART NUMBER 67-16222 (scroll down to page 198), but it's a hefty price of $65.00 plus shipping (and taxes if that applies to you). I've not personally seen it so I can't comment on how "correct" it is, but if THEY have it, maybe others do too.
Of course, if you're not looking for "correct", you should be able to find a replacement at just about any of your FLAPS (
Friendly
Local
Auto
Parts
Stores).
Ed