You can use the T420/T520's keyboard in a T430/T530 with modifications to the firmware, some plastic around the keyboard part itself, and the ribbon cable (just pin isolation with tape). It lets you go with Ivy Bridge over Sandy Bridge.
I have a T430 with the T420's keyboard and it lasted me 7 years of daily use before battery life became too big of an issue for me (even with a single DDR3L RAM module and a slice battery), so I put it aside. The typing experience was really excellent.
Upgrading the CPU to a quad-core model (ideally one that consumes 35W over 45W) is one of the best upgrades to make for anyone still using these machines.
I have a T430 with the T420's keyboard and it lasted me 7 years of daily use before battery life became too big of an issue for me (even with a single DDR3L RAM module and a slice battery), so I put it aside. The typing experience was really excellent.
Upgrading the CPU to a quad-core model (ideally one that consumes 35W over 45W) is one of the best upgrades to make for anyone still using these machines.