4.3 v-6 rebuild or replace?

First of all, I would like to apologize for posting to the 4x4 group, when I only have a 4x2. Houston Road Runner doesn't have just a Chevy Trucks group. I hope you don't hold that against me.
I have a 1989 C1500 4x2 with the 4.3 v6 and 5 speed standard transmission. I bought it in 1992 with only 60,000 miles on it.
the engine internal components are all original, the clutch is original and the transmission is all original. the truck now has about 300,000 miles on it. that's a guess, my odometers work only part of the time...but that's another email.
like I said the internals of the engine are all original, the only things I have replace are the starters, AIR pump, water pump, fuel pump, alternator, filters and fluids. it's been a really low maintenance truck.
as far as I can tell, there is no oil in the water and no water in the oil. it's never ran hot and never been dogged, I bought the truck attempting to not have another car note for a really long time, I know it's a pipe dream, but I'm so tight I squeak. the body is in good shape, it needs a paint job and very little body work (a crack in the fiberglass fender) and there is no rust.
Recently, I had to change the catalytic converter, because my other one plugged up and blew off, literally, it was a factory original slip on.
After a week of service, the new one is about ready to do the same. I'm sure I have oil blowing by, I see the puff of white smoke every time I start it after it sits a couple of hours. I'm sure the engine is burning rich as well. I need a new MAP sensor, but I haven't gotten around to it.
I would like some opinions and information as to whether or not it is worth rebuilding the engine. or if I should get a rebuilt/crate engine. what are the pro's and con's of both?
I don't have the space to do it myself, I would love to. if I can get it rebuilt, where do I start? what questions should I ask? what are your opinions for quality components to get me another 300 - 500k?
I'd like to keep the original block, but with 300k on it what potential long term issues, if any, am I looking at?
if you need more information, please feel free ask, I'll let you know whatever I can.
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I would get a new crate motor, you've got your moneys worth out of the old one.
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Replace the oxygen sensor if it is original, they deteriorate over time and will give a bad signal to the computer.
nanook wrote:

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