You might take a look at the left manifold that came on several years of Chevelle and most trucks from the mid 70's. It drops down below the spark plugs and has an outlet near the rear of the manifold, about 2/3rds back. Someone did a post a while back that it was the way to go for AD trucks. It might work on the earlier ones also.
Classic industries has a good selection in their catalogue. Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine