If you pay a shop to do the rebuild, probably in the $2400 range. This does not include R&R the engine.
The cost to rebuild a Chevy 305 engine typically runs between $400 and $800 depending on the level of rebuild. This will greatly extend the life of the engine and improve performance.
I just got an estimate of $2200 for a complete rebuild of my Camaro 5.7L / 305
250,000kms
Since this category is 305-350, I'll have to assume that YOUR engine is one of the two mentioned. The 1990 Chev 305 and 350 did not use a timing belt. They used a timing chain, and unless something really odd happened, you should never need to replace the timing chain until you rebuild the engine.
If oil pressure is low, compression is down on one or more cylinders or you encounter knocking, blowy-by or crankshaft oil leaks, it's about time to rebuild the engine.
The cylinders would need to be bored to 4", which would probably make the walls too thin.
about $2000
bout 280
You can change your 1986 305 cubic inch pickup engine from a carburetor to fuel injection. The problem with doing so is the cost. It might cost more to do the change than it would to purchase an engine.
5 quarts
That totally depends on how MUCH MONEY your wanting to spend. Myself I wouldn't spend any money on a 305 engine. I would get me a good 350 engine to build.
Need to know the year of engine and size of engine that you are asking about. But first you need to know this. A 5.7L is a 350 engine. and a 5.0L is a 305 engine.