Hi Scotty,
I am looking to replace my 1991 Toyota Previa rwd minivan. I don't have a lot of money so am looking towards a 2000ish Chevy Astro or GMC Safari awd minivan. More than likely a private party purchase. Wondering how many miles for the 4.3 and tranny and running gear is too many also what else should I be looking for? Or should I just forget them and go with a Toyota Previa or Sienna awd?
Starting out with a decades-old Astro van is not a recipe for a vehicle that's going to last you very long. Really, how much longer do you realistically expect one of those to last? Unless you get very lucky and find a low-mileage specimen you'll be buying a vehicle that's already well worn-out.
A Sienna would be a much better choice.
looking towards a 2000ish Chevy Astro
a tired old thing like that will be falling apart. Save up for a newer Sienna.