Does anyone know the size of the intake plenum to intake manifold O rings, or are do I have to get them from merc?

Also the size of the O ring for the oil passage under the # 4 bearing cap?

The o ring for the rear bearing cap comes in the box with a fel pro rear main kit.
The intake o rings you're going to have to get from merc

Try here:
http://www.offshoreonly.com/forums/d...m-o-rings.html

O-ring on the main cap is not necessary.

It makes guys that run thin oil feel warm and fuzzy..

You have a point there. I wonder if everyone really knows what you mean by that statement...

Thank you so much. How about the O ring for the oil filter adapter? Its about 3 1/2" or so

There is a cut in the block and the o-ring doesn't cost jack..Why would you not just use it ?

i AGREE.

http://paceperformance.com/i-6485828...-oil-seal.html

#6264902 - Big Block Chevy Gen V & VI Rear Cap O-Ring Oil Seal

$1.19 FROM gm / gmpp DEALERS.

It's not needed the old big blocks never had it. I didn't put it back in my Dart block the last time I put it back together. It's not needed. If it makes you feel better have at it.