I am sure others will chime in here. Either option will work but to depends how much time vs money you want spend.

option 1, if it where me I would got that route but tear down the engine and pressure test the block and refresh it while it was out. No way I would install it as is, you could just end up in the same boat. You could also just get a known good block and swap internals over. If you can’t do this yourself see option #2

option 2, AB block is very expensive and they will only warranty if you have a shop install it. So this will be $$$ but more of a better shot of not having problems.

Edit: sorry missed the part about no cost to you. I would go the AB route in that case. If they are only giving you 30 day warranty on the used engine then it’s not worth the risk in my mind. I assume the shops liability ends for any other issues after 30 days.

 

The AB option I will have to pay the difference in the cost between the used engine and the AB long block. I figure the in and out costs between the used engine and the AB long block will be a wash.

 

I'm going to be replacing the engine with a 4.6 long block from AB. What else should I be replacing while the engine is out and things are easy to get to?

 

Starter, CPS, repair all the cracked looms.

 

Perhaps relocate the ignition coils?

 

I'd recommend turner engineering instead. I know several rover-specific mechanics who will never buy an AB block again. poor quality machining. turner does it right but it ships from England as a short block.