exhaust manifold application???

[Mr70]

That #14045176 R/H Ex. Manifold is a 1967-87 Truck 396/402/454 application.There are many of these out there and more so now that the #178's are starting to dwindle down.As you said,they look identical,except for a few minor details aside from the casting No.
I see these at swaps asking 50.00 with no takers.They came with & without A.I.R. provisions.

The #3909879 & #3916178 Ex.Manifolds were used on Most but not all Big Block Camaro-Nova-Chevelle-Monte Carlo-Elco-Impala from 1967-1970,with & without A.I.R provisions.From 325HP all the way up to 450HP.
Check Alan Colvins book for exact motor applications.

The 1970 dated applications were unique,in that only they have a machined pad with a dimple on the #879 manifold's #1 ex. port only.Because of this,they are quite costly today if recognized.
This feature was continued on the 1971-72 L/H Manifold,but the casting No. changed to #3989343.