E-3 REPLACEMENT
You really think the F-35 has anything like the observational power of the radar system fitted to the E-3, or even the Hawkeye? You might want to go check your sources over...
The Russians have been flying radomes on airframes almost as long, you refer to the Shaanxi turboprop and the Ilyushin 76, there was also a heavily modified Antonov Coaler.
Look up the Japanese 767 AEW, the Australian Wedgetail program, and quite a few others...even the Iraqis modified an Il-76 off their own back for this once.