Would I be ahead in parting out, or selling whole?

$350 on a private party sale is about top price for that 5.9 around me. There are tons of them around since the transmission is the weak link.

Salvage prices in your area:
Walk in retail for that motor with 164K at Don Schmid Auto Salvage there in Wichita is $600.71.
G & R Motors in Wichita had one with 105K for $650.
Rocky Hill in Coffeyville has 7 in stock for $450.
Sandlian Iron & Metal has 4 for $450 and with mileage as low as 150K. That is just part of the list/

Salvage prices on the computer run between $65 and $125.

Transmissions are scarce and are bringing what the engines are. There is only 4 showing in the state of Kansas.