250 CID questions

[ctumbler]

Guys -

A few questions. Recently picked up a 66 C10 with a 250 with a 700r4 behind it. Nothing on the truck quite lines up, and there is a ton that needed to be sorted. From the casting numbers on the block and the exhaust manifold it looks like this is an early 70's 250 - no idea on the 700r4 yet. First thing I am tackling is the rear end and tranny - the drive shaft is way short and the rear end fluid looks like river water, also the TV cable was melting to the exhaust manifold. In looking at getting the TV cable hooked up I noticed a few things I cannot explain on the engine block and exhaust manifold. It looks like there is a rail tapped into the block along the side of the manifolds - it is pinched at the firewall end, and capped at the radiator end - pictures attached. Any idea what this is all about?? Can I pull this and plug these holes? Also - some sort of vacuum end tapped into the end of the exhaust manifold that runs back to the distributor??

Any help would be amazing as I try and get this project moving in the right direction.

Thanks

C