I have been so long without working heaters (8 + years now) I don't really now what to expect. My last aircooled cars with heaters were entirely stock ('76 Beetle and '70 Fasty), and worked perfectly.

The '67 is far from stock.

1. I have virtually new heater boxes to setup

2. My deck-lid does not have vents

I am concerned I will go to the trouble of getting a heater box friendly exhaust to learn it fills the cabin with the smell of fuel and oil. Especially with twin Dells.

What are your experiences with heater boxes and twin carbs?
Did the cabin smell like an engine bay?

Thanks
Wayne.

I have owned a lot of Vw's over the years and also my 61 Ghia since 1967,i have had no problems with oil smells in the heater system. All it requires is a bit of time and care ensuring there are no leaks (oil or exhaust) and that the cables/flaps/air flow tubes are in good condition.
There are a couple of different systems and the better one is the one with the fresh air supplied from the fan housing,twin carbs / engine lid vents shouldn't make any difference as the air is supplied by the fan.

Wayne

do what I have done nice exhaust ( Vintage Speed ) and heaters with big J pipes for the 2 rear cylinders we talked VS into making the big J pipes for a test and they work great

works well and nice heaters