I got a good deal on a 4.3 from a Astro and 350 trans with adapter. My Q. any helpful hints/mistakes made that would help me out. Plans are Aftermarket radiator with elec. fan and trans cooler, Shifter not decided yet, after market intake, manifold, and headers.

I have a stock 89 toy with a work box on the back and MSD ignition.

 

Start reading.

https://www.yotatech.com/forums/f163/

And order a conversion guide from advance adapters. I think you can download it too, but its nice bathroom reading material

 

Agreed READ READ READ AND READ AGAIN! There is a lot of info on 4.3 swaps and there are a lot of build up threads with 4.3s. Use our search function and you'll see what I'm talking about.