V6 Triton auto - manual conversion possibly diesel

[OZBMX]

G'day guys I have a v6 triton with 440 k's the motor still plods along but probably a bit tired and more importantly seems to have quite a substantial leaking issue, but more importantly the automatic has a problem with the pump, so some days plays up, sometimes runs alright, it may be repairable but I'm contemplating just converting to manual as I prefer to drive manual.
Also for cost reasons I'm curious about a turbo diesel motor.
going bigger one thing but this is first time the concept of a smaller motor has ever crossed my mind, be handy to have a 4 as opposed to a 6 and an 8
anyway has anybody ever done any of these possibilty or how different is the motor/ gearbox's if I can get one out of a say pajero challenger I know atleast the motor's are different but suspect their useble. I have a bit of experience knowledge, converted my fairmont to manual along with various other bit's and pieces I've done in the past on my cars but don't want to go out and get myself stuck buying something thats going to be a major problem e.g. say the the firewall on a manual cars completeley reshaped or crankshaft is different so can't just change the gearbox
anybody know if transfer case is different auto manual.
I understand issue like challenger tailshaft is a hair different etc. but thats easily fixed.