BN-137A
| 9 bolt cast iron w/2 bolt heat & oxy in manifold inlet |
| 3 bolt outlet |
| OEM# 21015313 |
BN-137B
| 8 bolt cast iron w/2 bolt heat & oxy in manifold inlet |
| 3 bolt outlet |
| OEM# 21015312 |
BN-137C
| 9 bolt inlet, 3 bolt outlet |
| 1 sensor in manifold |
| OEM# 12571601, 28703 |
BN-137D
| 7 bolt inlet, 3 bolt outlet |
| 1 sensor in manifold |
| OEM# 12571605 |
BN-137E
| 9 bolt inlet, 3 bolt outlet |
| 1 sensor in manifold |
| OEM# 12571601, 28703 |
BN-137F
| 7 bolt inlet, 4 bolt outlet |
| 2 sensor |
| OEM# 12578648 |