Do not let that smoke out!
CK5
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Watched it. Confirmed it's PFM. 
Yeah in those years Chevrolet was c10, c20 and c30.
GMC was c15, c25 and c35
Cool. The only time I remember seeing the "15" designation for GMC was on the little pick ups; S10 vs S15.
1960-66 GMC the 15/ 1500 designation was a 3/4 ton truck.
I stand corrected.
It's weird though Chevy did c10, 20, 30 and gmc did c1000, 1500, 2500.
That was 60-66
Then in 73 they changed to how we know today 1500, 2500 and 3500.
I'm not sure what year they changed between 67-73 as I have never paid attention to the expensive years between my favorites. But my wife did have a 72 GMC K2500 that was a 3/4 ton.
Well according to wikipedia's very reliable information
it started with the 67 body style, since then it has been steady no changes.
I think that's when they stabilized the GMC & Chevy trucks basically being the same. At least mechanically.
Although I read here or in another board the late 60s GMC pickups were standard with rear leafs and optional trailing arm but the Chevy trucks were the opposite.
Although I read here or in another board the late 60s GMC pickups were standard with rear leafs and optional trailing arm but the Chevy trucks were the opposite.
Oh and I forgot the good news about the recent work! I can see the very bottom of the shiny different cover walking up to the truck. I call that a win! 
Looking to get the timing chain replaced along with oil pan gasket and rear main seal.
Any opinions on rubber vs silicone vs viton rear main seal materials?
Any opinions on rubber vs silicone vs viton rear main seal materials?
I vote rope style. Go old skool!
I am a fan of Viton anywhere it freezes.
Hard no.
We did rope seals in the Navy, no thanks. Interesting. It stays softer at the lower temps?
That has been my experience. And wear longer. Had to go vinton seals in everything hydraulic in Colorado. Did not need them in Ca.
If I had the choice I would go viton in any kind of weatherHard no.
Interesting. It stays softer at the lower temps?
My inclination is to choose the more expensive option in these kind of cases (within reason) but I wanted to get opinions on the viton.
This is a MAW project. I have to replace the timing chain. I need to drop the oil pan and clean out all the pieces of nylon that broke off the timing gears which caused the issue with the chain hitting the cover. While the pan is off, I might as well address the rear main seal leak. And I have to remove the water pump to swap the timing chain, so I'm going to preemptively replace it.
I am holding back from MAW on the balancer and oil pump. Although I'm more on the fence about the oil pump. I know I'm going to be cleaning little pieces of nylon out of the pickup screen. But really it should be fine otherwise. Unless the plastic collar for the distributor shaft is busted up. Maybe I should go ahead and MAW the shaft regardless.
This is a MAW project. I have to replace the timing chain. I need to drop the oil pan and clean out all the pieces of nylon that broke off the timing gears which caused the issue with the chain hitting the cover. While the pan is off, I might as well address the rear main seal leak. And I have to remove the water pump to swap the timing chain, so I'm going to preemptively replace it.
I am holding back from MAW on the balancer and oil pump. Although I'm more on the fence about the oil pump. I know I'm going to be cleaning little pieces of nylon out of the pickup screen. But really it should be fine otherwise. Unless the plastic collar for the distributor shaft is busted up. Maybe I should go ahead and MAW the shaft regardless.
Just noticed something interesting. For the BBC application Fel-Pro calls it Viton, but for the SBC it calls it Fluoroelastomer. I want to say Viton is a type of Fluoroelastomer.
You MAW pull the engine and roller cam it. Roller rockers. AFR heads and put 5 pounds of boost in it. M.A.W.
