yes it will fit, any smallblock Chevy intake from 86-55 are interchangeable, the 86 and newer have bolts that go staight down instead of on a angle
On a small block Chevy the distributor goes through a hole in the intake manifold. On a Pontiac the distributor goes behind the intake manifold.
intake manifold
yes
you have a coolant leak
No. That would usually be a 283, 307, or 327.
Yes it will as long as the 350 engine is not newer then a 1986
it could be a head leaking or the intake manifold, if its coming from the very top its most likely the intake manifold gasket
25 to30 foot pounds
That is the intake manifold casting number from a 1970 350 CI 300 HP engine.
It was usually bolted to the intake manifold in those cars.
There is no difference,,,
Yes you can upgrade to a 350 but only if it is an Oldsmobile 350 and you will need to use small block olds toronado intake from a 307 so you will have hood clearance-you may need to enlarge ports in intake to match 350 head ports but probably not much. You can use your 307 heads on the 350 but I would put bigger valves in those heads before I used them with a 350 and porting would not hurt if you want much performance. The Olds 350 will have a lot more power stock than the 307