I wouldn’t worry about trying to tie together into a common line if that’s what you mean. Just route both under car.
If you park outdoors you’ll be fine.
If you’re parking in a garage you should look into finding the expansion tank and charcoal canister. I had to go this route - like your car, mine came to me “fixed” by DAPO who got rid of the evap system when they installed carbs.

Full disclosure: I was a DAPO back in the 80s with my first 914 and ditched the evap stuff when I went to carbs . . . And dealt with occasional gas smells.
For what it’s worth, by having tank vented to atmosphere, it’s not great for the environment and over time your most volatile parts of gasoline evaporate off which I’d rather be burning and making power with instead of smelling up the garage.