The 400K drive in the Lisa 2/MacXL are the exact same drive family. The Lisa drive did not have the same auto eject feature ... it is triggered on shutdown regardless if a disk is in the drive or not. The Mac will only auto eject if a disk is in the drive. Either way, it will work fine until you have a crash with the disk in the drive, then you'll have to pull the front panel off and press the manual eject switch.
If you are able to try it, please report the results, or if anyone else knows for sure ...
As for the 800K drive, it usually requires upgrading the ROMs and using MacWorks Plus. However, since one model of the 800K drive will boot a 128K & 512K, P/N MFD-51W-03 (found in the The Apple 3.5" External Drive P/N A9M0106 as listed on above ebay and later Macs), There is a good chance that the Lisa will be able to use it as well. See this thread: http://68kmla.org/forums/viewtopic.php?t=1492 as I suspect if it works all the same principles will apply. Mainly, it requires a special cable to avoid constant drive access. If your Mac Plus is a later model, it may well have the MFD-51W-03 which is easily identified by red numbers on the side of the drive, as well as the proper cable. An 800K drive SE & Mac II will most likely have this drive, but not the cable since the later Macs did not supply the speed control signal on the internal FDD.
One thing you can do without a floppy drive is run the secret Built-in Service Module. Turn on the Lisa. At the end of the kernel test (when you hear the first click), hit any key except caps lock. At the end of the module test (when you hear the second click), hold down the Apple key and press "2". The Lisa should beep 3 times and present an error box – ignore it. Hold down the Apple key and press the "s" key. The resulting service menu should be self-explanatory.
FYI, Larry Pina suggests you can use the same Hard Drive used in the SE in the Lisa and plug it in in place of the Widget. I know absolutely nothing about the Widget, but I found this somewhat surprising. Anyway something for you to investigate or for someone else to expound on.