BB exhaust manifolds

[Moparfun]

Hello there!
I have a pair of BB exhaust manifolds and I don't know what they are from.
They have the newer style flanges (not flat) and the part numbers are:
#3830800 drivers and #3830820 passengers.
Anyone know?

 

[Moparfun]

The drivers side has a rear dump (past the 4th cylinder) and the passenger's side dumps between the 3rd & 4th cylinders).

 

[Redpolara]

From what I could find,they're both mid 70's truck/motor home manifolds.

 

[yellow68runner]

judging from the pictures . . . . .