Can anyone tell me what the factory correct intake manifold and bellhousing to block bolts look like? I'm trying to do a concours restoration on my 1969 Firebird 400 4-spd Convertible and getting mixed info on what bolts were used on the engine and tranny. ThePartsPlaceInc sells what they call "factory correct" bolts that have a "O" surrounded by 5 slash marks on the head and they said the intake and bellhousing bolts were the same. Firebirdcentral.com claims their bellhousing bolts are factory correct and have a "M" in the middle of a "O" which is surrounded by 3 slash marks. Motor City sells original intake bolts on Ebay that have a "M" surrounded by 3 slash marks.
I know strange things were done while assembling these cars back in the 60s but I'd like to get my car as close to the norm as possible. It is PHS documented with 3 invoices (believed to have been a show car for region dealer events, then executive driven and then invoiced for public sale through a dealer several months later). The engine was built the 2nd week in July, body number 4, car assembly number 640. Thanks!

Never thought about keep'n hardware separated and marked.
Just tossed everything from same engine in a box and put on shelf.
Had a 69, so look for that box 2nite lol.

Found intake sets from 68/69/70.
All have 3 lines but different letters(B, C, P)(date coded?)
Forgot.
Still need to find bellhousing bolts.
Think thier all in one can...

The bellhousing and intake bolts are the same size: 3/8" - 16 x 1 1/4" long and both have a flanged head. Including your input, I've heard of heads with 3 slash lines and either A, B, C, L, M or P in the center. It looks like we're getting closer but it still seems somewhat of a mystery. I wonder if there is a member with an unmolested V8 survivor firebird.
Thanks for taking time to look!!