I've rebuilt MT except for Char Gen, which is close to stock.
CT character gen but lots of level 0 skills for service and a couple of changes to skills tables - promotion through enlisted ranks and 2 skills per term for others
skill throws using TTA guidelines plus MgT 2e boon/bane
combat is T4 based
Setting wise:
proto-Spinward Marches (adventures of the Bloodwell)
Learning/building/doing T5, which requires a lot of home brew.
I moved from T4 to T5 when I got my hands on the BBB. I still use all the support material from a variety of versions, but up until now have pretty much run all my "contemporary" games in the Spinward Marches using CT, MT and now T5. The only deviation in location was with T4.
How does combat work in T4?
How much Traveller is in your Traveller gaming?