Hello and welcome to the Forum
This topic has been discussed before. Here are a couple of Forum threads discussing the viability of T42/T43 drive swap: viewtopic.php?f=2&t=85112
General consensus seems to be that it's a little problematic. (T40 to T41 to T42 drive swaps are very easy as discussed here: viewtopic.php?p=675783#p675783
but T40/41/42 to T43 (or vice versa) doesn't work well. There was a major hardware/software/firmware upgrade between T42 to T43 generation. If you tinker with it, you might eventually get it to boot up but the T43 setup is not really optimized for a T42p, so you might not only face blue screens now but unexpected blue screens later on. In my opinion it won't run as fast or as smoothly as a fresh T42p-specific installation. My own personal experience of drive-swapping between all of these models bears this out also.
240, 380Z, 390X, 570E, 600x, 701C("The ButterFly"), 770, A20...22,31, G40,41,
R32,40,50,51,52, R60,61, SL410/510,T20...23,30,40...43, T60p UXGA,T61,T400,
TransNote, X20..24,31,40,X41T,X60,61,X60/61T, Z61t, W500
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