LS engine question

[misternash2]

i talked to one of my buddies that works at a salvage yard. he made me two deals. just curious what you all thought about it.

1. 5.3 and 4l60e out of 01 silverado. 90,000 miles $1000 bucks

2. 6.0-04 model year 60,000 miles and a random 4l60e for $1750

will a 4l60e hold up to a 6.0 or should i upgrade to a 4l80e?

what are some potential that i'll have with the computer not buying a matched up motor and trans?

i'm mostly looking for mileage, but 6.0's got bragging rights!! i'm pretty interested in going 6.0 if it's not gonna be a major PITA getting it all lined out computer-wise.