what do you find is a reasonable deal for a used 8.1 (L18)?

[324matt]

Since my stock 350 is using more anti freeze and oil than fuel as of late, I have decided to do the 8.1L swap/conversion vs. a LS swap or install a crate 350 or 383. The torque numbers and all of dirty Larry's threads have me convinced. So far my search for an engine has resulted in these prices. One of my concerns is the mileage. How many miles is too many miles for one of these engines, before a swap would be mute?
EBay $1500 + 300 core for a 144k motor
Ebay $2000 + core for a 115k motor
LKQ $1100 + 375 core for a 144k motor
Rv salvage $3000 no core for a 10k motor.

What are your suggestions or thoughts? I'm hoping that someone with experience will chime in on this one.