547975 3 Versions
General Motors Casting Number 54975 Bellhousing
The "975" is an aluminum bellhousing for B.O.P.
(Buick, Olds and Pontiac) engines.
Warning : I have found at least 3 different versions
of casting #547975 clutch housing.
I have one version that is identical
(except for the casting number)
Another version has the "peanut" ball stud boss
with the upper area tapped (standard B.O.P.).
And yet another version has the "peanut stud boss
tapped in the lower area (78-87 A & G Body)
Transmission View
In this picture you can see the two starter housing (ears),
which allows it to fit Buick, Pontiac and Oldsmobile
engines. And the extra holes for Ford transmissions.
.

Part # 1
Some versions have the casting number that is cast
.
Part # 1
Some versions have the casting number that is cast
into the drivers side starter "ear".

Part # 2
Some versions have the casting number that is cast
into the drivers side, under the z bar mounting
bracket holes.

Top
The "V" at the top of the casting is another B.O.P.
identifier.

Fork side
Top
The "V" at the top of the casting is another B.O.P.
identifier.
Fork side
The fork hole is the standard (Approximatly 3" x 2 1/4")
size.
Bottom
This bell takes the same type of,
one piece sheet metal clutch inspection cover as
the "581" and "882" clutch covers,
that is held in place by three 5/16"-18 bolts.
Passenger Side View
Clutch Side Version 1
Here you can see the two starter "ears" and the
engine mounting flange, with six clearance holes
for bolts and two dowel holes.
Inside View Version 1
This picture reveals the fork mounting stud location
and beefy reinforcements around all mounting holes.
Notice: The single stud mounting boss.

Clutch Side Version 2
All mounting holes are the same for all three
versions.

Inside View Version 2
This version has the double stud boss with the
This version has the double stud boss with the
tapped hole in the upper area. This makes it a
replacement for casting #9785581.
Quick Reference
Size: 166 tooth flywheel
Engine Bolt Pattern: Buick, Olds, Pontiac
Transmission Bolt Pattern: GM and Ford
Transmission to Bellhousing Threads: 1/2"-13
Center Hole Size: 4 5/8"
Ballstud Threads: 13/16"-16
Inspection Plate Bolt Threads: 5/16"-18
Face to Face Measurement: 6 5/16"
Starter Mounted: No
Starter Nose: Dual
Note: all measurements are approximate.
Disclaimer:
Factory correct applications are your responsibility. GM made part and part # changes with no rhyme but a reason (no production interruptions at any cost).
Application charts are for replacement parts that were available at the time of parts book printing, and when possible model specific assembly manuals.
My observations come from the parts I have in my collection or other reliable sources your parts may differ.
If Factory correctness is your goal, do more research, join car clubs,
forums and buy an assembly manual if one is available for your Project Car (you wont be sorry).
This is a fun and interesting part of the hobby!