Since you don't give a year or the car, is it properly vented, aka a PCV valve and valve cover breather on the other side? Excessive crankcase pressure can cause leaks like this.

 

Sounds like you have a pan gasket leak, not a rear main seal leak. Rear main seal is contained inside the block and rear main cap. Pan gasket seals between the pan and exterior of rear main seal.
To repair either leak, you will have to pull the engine. Yes, it is possible to pull the pan with engine in the car, but it is a total PITA. Once you do that you can determine where the leak is coming from. Use a correct, good quality gasket, get all the parts clean, really clean. Often time old gasket remnants are very difficult to see and can really cause problems. Install gaskets to manufacturers specs, torque bolts to Chevy specs. Check pan flatness with straight edge. I have had great success with Permatex Aviation gasket sealer. Total pain to get off your hands, but best sealer I have found.
If it turns out to be the rear main seal, check the crank carefully for pitting in the gasket seal area. Put a small amount of good gasket sealer on the ends of the main seal where they join each other.

 

I'm sorry it's an older 1968 block. It does have a breather and PVC thanks for the input!

 

PVC with another hose going from the valve cover to the air cleaner??

 

Usually you clock the rear main seal a bit and put a dab of sealer on the mating ends. If you can see if you can see between the flexplate and block and make sure its not leaking out of the rear galley plugs. I think you can get a flouresent dye you stick it in you oil and use a black light to see where its leaking from

 

x2 on the dye and the light. Clean the entire engine drive for a while then check it out.

 

Had oil in the same spots and finally tracked it down to the back edge of a valve cover. Had stamped steel covers and cork gaskets at the time. Changed out to cast aluminum with silicone gaskets and no more leak..... May not be your issue, but it could be a cheap(er) fix if the same. I was expecting rear main, etc... on mine also. Good luck!

 

Thanks for the help

 

Had a friend take in his 1985 truck with a 305" that i tweaked the carb and distributor on
That 305 would roast the 255-70-15 tires and got 15 mpg in that truck with his foot in it

He had a friend that owned his own shop , had this friend build a 350" for him for more power.
I told him a stocker 350 smog headed piston down the hole a mile will be a turd.

He said his friend was doing it up good.

Yep he did it good .. with red silicone on everything.. stained every inch of his driveway and got 10 mpg and could not spin the tires..About 6 months of back and forth with no gains he sold that truck and got a 1991 350 powered truck...

Do you see any red silicone?
I remember about 6 years ago people complaining about rear seal leaks felpro seals .
Seems there were some issues with them.. I was in the same boat.
Someone mentioned that they use silicone on the backside of the seal to have it conform or but up better.. After 2 failed attempts i tried the silicone on the backside.
That fixed it.. Ultra black is what i used.

I then had a front oil pan leak i could not cure.. i was using the 1 piece felpro.
It was pooching out funny in that front timing cover lip.
I cut all that lip back side off the timing cover except the bottom 1" or so.
Cleaned with thinner really well and then applied Ultra Black on both sides of the blue seal.
NOT a drop in 10,000 miles.
I really do not like to silicone stuff ..But that Ultra seems like good stuff and i was at my wits end.
You know I built many engines that never leaked and I never stuck silicone on the parting lines of a rear seal...I always wondered if it was really needed.

Kind of like cotter pins in tie rod ends and ball joints.
I have never had to tighten or back off a nut to get a cotter pin out.
And when the nut is finally loosened you need to beat the thing apart.

Connecting rod bolts many many years ago had cotter pins in them. Some engines.

Things to think about.