When is it time to upgrade the truck?

with only 870,000 miles most of it should be in good to fair shape still . rebuilding sounds like best choice to me... btw we have guys with 03 04 petes they just rebuild and keep going 2 of them are well over 3millon km (2millon)miles and boss swears they are the trucks with least problems at our company pulling tri axle weights

 

You're going to spend close to $20,000 on anything you buy...plus you still have to buy it. If it's a 379 I would rebuild in a minute. If it's that plastic model that looks like the T2000 KW...well I'm not a fan and they don't really hold their value.

I missed why you think your trans needs a rebuild. I have 1.8 million Kms on my 13 and I don't plan on a rebuild anytime soon.