305 Chev blowing smoke after rebuild

Hey guys, first post and all that...
I did a bottom end (main and rod bearings) rebuild and new headgaskets on the 305 in my '79 C10, motor ran fine for about an hour and then started blowing smoke out the Driver side exhaust. I pulled the plugs on that side expecting to find a blown oil ring on one of the pistons but found oil on all the plugs. My current thought is perhaps the head gasket slipped when I was installing the head on that side and there's oil blowing into the bore. There's been no loss of power at all, motor runs just fine but as I said, it's blowing smoke only on the driver's side.
Motor is stock 305 with a 350 intake and a Rebuilt Rochester QJet. Dual 2.5 Exhaust and a stock TH350 trans. (Some torque converter drainback problems but that'll be fixed soon too)
Don't even bother with replying if all you can say is "Get a 350" I've got one sitting on an engine stand that I'm rebuilding but I want to fix the problem with the 305.

try retorking the head. sounds like a head gasket to me. sucking some oil. does it have a lot of crankcase pressure ?

Oil pressure gauge runs pegged out all the time. It always has, shows 60+ psi when running. The only time I've seen it below that was just prior to the rebuild when it would drop way down at the lights.

If you put a new intake manifold on you might have a warpage problem with oil being sucked into the valleys. It happened on my 305.

Nope,
Same head and intake setup that was on it prior to the rebuild.

i would do a comp. check wet and dry.

Probably a long shot, but did you forget or damage the oil seals on the valve stems?

Did the motor get hot when it went out? Sometimes you can wharp a head and not tell. Not tying to sound silly but I always check the ovious first, head gasket in correctly, oil rings in correctly? Did the cylinder's get honed? I am sure that you have done all that already. I am haveing heating problems with mine, so I too am going back to the drawing board.

I'd guess the intake manifold gasket shifted when you assembled the engine, and is sucking oil from the valley.

Ok here's my first thought....Some builders assemble with oil...(I do) Is it possible that its just blowing out excess oil or something? Every motor I have ever built smokes for a little bit when i first fire it because I dip the piston, rockers, pushrods, lifters (sometimes i use cam lube), bearings, ect. in oil. Maybe I'm wrong but better to have ALL the bases covered.

Thanks guys for all the input.
I pulled the valve cover off again last night and had a closer look, buried way in the back the intake rocker arm on the last piston had backed the factory nut off and the rocker arm was no longer contacting either the valve stem or the pushrod... gonna get some new nuts for the rocker arms tonight and put them in, had to drive the truck to work today and there wasn't a single bit of smoke out the back. kinda intrigued cos there wasn't any rattling at all that would have alerted me to the slipped rocker arm.