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.
250,000kms
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.
If you pay a shop to do the rebuild, probably in the $2400 range. This does not include R&R the engine.
I just got an estimate of $2200 for a complete rebuild of my Camaro 5.7L / 305
18436572
Either a 305 TBI, 305 TPI or a 5.7 TPI
305 or 350
Depending how and where its driven,two wheel drive or four. but typically you should have no problem hitting 350,000k, it's recommended for a complete rebuild at 200,000k. Depends on how well you take care of it.
200
five quarts
The cylinders would need to be bored to 4", which would probably make the walls too thin.
You can, but it will kill the performance of your engine.