I joined and tried to list an item on there only to be rejected. It seems they only allow a certain few.
I left after no admin responded back concerning matter.
I was curious about your setup. Here is their video.
If you drop your tank and drain fill with water, you could drill safely for the return bung.
Then run the correct size line.
Besides, they advise not to have the return on top of pick-up.
I had similar issues years back with my C10 and I also assumed bad gas.
The culprit was the fuel pick-up sock that came off inside the fuel tank allowing it to suck up trash.
Edelbrock and many others recommends a non-steel core gasket for use with aluminum intakes as the low torque of the bolts does not sufficiently compress the steel core gasket.
https://www.edelbrock.com/intake-manifold-gasket-for-1965-1990-oval-port-396-402-454-b-b-chevy-7203.html
Which intake gasket are you using? Hopefully not steel core. The matching Edelbrock gasket would be good.
I would run a clean-out tap in all bolt holes and don't forget some ARP (or equivalent) thread sealer on intake bolts.
This coilover kit here is adjustable and can be put close to stock height and you could also use the watts link axle locater which is better than panhard bars which that allow some movement.
https://cachassisworks.com/p-3072-gm-73-87-c10-truck-bolt-on-4-link-coil-over-suspension.aspx...
This?
https://www.summitracing.com/parts/sum-200280
https://www.summitracing.com/search/part-type/throttle-lever-studs
Put the spring in big hole and attach it to something forward.
It looks to me like they used the whole GM serpentine kit like mine which comes with the correct water pump, ac compressor and power steering pump.
The kit includes all new bolts like you have.
I painted my WP black so it wouldn't rust.
Chain should not go around a beam it creates a weak link but may be ok with the weight of bed.
Beam clamp (or trolley) with a shackle is the correct way...