mono-plane

I have started sorting thru my parts for my F85 W31 ex-race car, in order to see what I have that might be original to the car. My bell housing is an aluminum BOP style with an irregular shaped hole (sort of looks like a profile of a house with a peaked roof) at the bottom of it, like an inspection hole? The number on the housing is 9785581.

Can anyone identify this piece for me?

As well the trans that I have is a Borg Warner (not the original M21 as per my documentation) 4 speed. I have identified it as a May 9th 1975 Pontiac piece. Is there a real good website to identify exactly what this came out of? It was behind a 400 or 455 likely? I have got all of the numbers/letters off of it and decoded some of this info, but many of the numbers I have no reference for.

Bluevista

I figured it may be Poncho with that tranny so I looked in the GTO resto guide.
It shows that part number 9785581 is a 1965-70 GTO aluminum bellhousing, I don't know if it may be used in other cars too but it does show it for the goats.

I would try the PY forum if you want to ask about any Poncho stuff, good site.

http://forums.performanceyears.com/forums/

edit: I should of looked in the Oldsmobile parts book too.

Shows the bellhousing is for a 1964 F85 V8, 1965-75 V8 and a couple of others.